In March 1999, he was appointed vice mayor of Dongguan, a city in Guangdong, but held the position for only two-and-a-half years.

In April 2007, he was promoted to party branch secretary of Guangdong Provincial Audit Department, concurrently holding the head position since March 2008.

In March 2015, he was appointed as party secretary of Shaoguan, another Guangdong city, making him the top political leader there.

[citation needed] In March 2017, he was transferred to the neighboring Hainan province, and he was appointed secretary of its Commission for Discipline Inspection, the Party's agency in charge of anti-corruption efforts.

[7] In October 2024, Lan announced that the Chinese government would issue 325 billion USD in special bonds to boost China's economy amidst a sharp property market downturn.

[8][9] In November 8, 2024, China approved a 6 trillion yuan (839 billion USD) plan to assist local governments in refinancing their substantial debt.