In 2011, Lin Gengxin played the role of 14th Brother in his first drama "Scarlet Heart", becoming a popular idol of the 80s generation. With this drama, he won the 6th Tencent Starlight Awards - Annual Film and Television Newcomer Award, the 2011 Sohu TV Drama Awards - Annual Best New Actor, and the 1st iQiyi Awards - Most Popular Male Actor Award.

In 2012, Lin Gengxin gradually made a name for himself by starring in TV dramas such as "The Traces of Xuan Yuan Sword in the Sky" and "Sister Standing at attention and walking forward".

In 2013, Lin Gengxin was nominated for Best New Actor at the 33rd Hong Kong Film Awards for his performance in the action film "Detective Dee: The Dragon King of the Gods".

In 2014, he won the Annual New Male Actor Award at the 9th Chinese Youth Image Forum for his love movie "You, My Desk mate"; From October to 2017, several films including "Rise of the Rascal Heroes", spy action film "Taking Tiger Mountain", martial arts film "The Sword of the Third Young Master", and fantasy comedy film "Journey to the West: Conquering Demons" were also released nationwide.

In December 2017, he won the Most Popular TV Actor award at the 11th Tencent Starlight Awards for his inspirational costume drama "The Legend of Chu Qiao".

In 2018, Lin Gengxin teamed up with Zhao Youting again in the movie "Di Renjie: The Four Heavenly Kings", which was released in July.

From 2020 to 2022, Lin Gengxin's modern dramas "First Encounter, Last Separation", "My Bargain Queen", and urban sweet comedy "Please Call Me Director" were broadcasted one after another.

On March 18, 2024, the Eastern mythological drama "Walking with the Phoenix" co starring with Zhao Liying for the second time was broadcasted.

On January 4, 2025, participated in the Tencent Video Starlight Awards and won the annual reputation as a TV drama actor.