In 2003, William participated in the International Chinese New Talent Singing Championship Hong Kong regional finals and won several awards. He was then signed by Emperor Entertainment Group (EEG) as a new talent and started appearing in TV shows as a host.

In 2006, William joined Sun Boy’z, a Cantopop boy group created by EEG, together with Steven Cheung and Dennis Mark and started adopting a dance-singer persona. The trio has recorded three albums in 2006 and 2007, but disbanded in 2008.

After the disbandment of his group, William began his solo career. In September 2008, William released his first solo album Will Power, and won the Most Popular Male Newcomer award at the 2008 Hong Kong Jade Solid Gold Best Ten Music Awards Presentation and Most Promising Award at the RTHK Top 10 Gold Songs Awards. The following year, William released his second solo album Warrior. He also participated in Dragon TV’s dance program Let’s Shake It.

In 2009, William made his big screen debut in crime thriller Overheard. He was cast in his first lead role in Hi, Fidelity (2011), which was showcased at the 35th Hong Kong International Film Festival.

From 2010 to 2013, William released four more albums, namely Do You Wanna Dance (2010), Heads or Tails (2010), WOW (2011) and Pop It Up (2013).

In 2013, William began to shift his career focus to Mainland China. He filmed his first Chinese drama, The Four, an adaptation of Woon Swee Oan’s novel Si Da Ming Bu. The drama was aired on Hunan TV in 2015.

In 2015, William released his first EP titled Waiting, which is also his first Mandarin album. Waiting was a commercial success and achieved platinum certification in sales. The same year in November, he released his self-composed single “1121”.

In 2016, William released the single “Plan W”, which topped local music charts and reached ten million downloads in 12 hours. On 27 August 2016, William embarked on his first solo tour Inside Me which kick-started in Beijing. It was subsequently held in the cities Shanghai, Nanjing, Chongqing and Guangzhou.

In 2016, William starred in the tomb-raiding drama The Mystic Nine, which serves as a prequel to the popular web drama The Lost Tomb by Nanpai Sanshu. The Mystic Nine achieved success, placing first in television ratings and setting a record for the most online views garnered in a day, and has accumulated over 10 billion views. William gained a surge in popularity for his role as Fo Ye, and was named the “Person of the Year” at the iQiyi All-Star Carnival. The same year, he starred alongside Jessica Jung in the romantic comedy film I Love That Crazy Little Thing and featured in Guo Jingming’s fantasy blockbuster L.O.R.D: Legend of Ravaging Dynasties.

In 2016, William was appointed as the first Chinese ambassador of the NFL China.

In 2017, William starred in the historical fantasy drama Lost Love in Times.

In 2017, his wax figure dressed up as his role in The Mystic Nine was added to Madame Tussauds Shanghai. In 2018, a second wax figurine dressed in his concert attire was added to Madame Tussauds Beijing.

In 2018, he acted as a dance mentor in iQiyi’s reality online street dance variety program Hot Blood Dance Crew, as well as a mentor in Dragon Television’s talent scouting program The Next Top Bang.

In 2018, William headlined the war epic film Genghis Khan, as well as modern romance drama Only Side by Side with You and crime action drama Age of Legends He also starred as a supporting role in the war film Air Strike.

In 2018, William’s new brand Williamism collaborated with other companies (New Era, Reebok, UCCA, Aftermaths) to produce his own brand of caps, shoes, T-shirts and skiing attire.

In 2019, William featured in the hit rap song “Wild Wolf Disco”.

In 2019, William starred in the romance film Adoring.

In 2020, William was cast in the historical fantasy drama Novoland: Pearl Eclipse. His upcoming works include cyber security action drama Dancing in the Storm and fantasy film The Yin Yang Master.