He joined the Green Gang, the most powerful secret society in Shanghai, and eventually make his way to the top as the ringleader of the gang. He orchestrated his rise to power after the arrest of his predecessor, Huang Jinrong, by the Shanghai Garrison command.
He soon became known as the "Jung Shi" or "Boss of the Underworld."
Under Du's leadership, the gang controlled gambling dens, prostitution, and protection rackets. They also were a leading opium trading group (opium dealing had been a profitable business since the British introduced it to the China in the 1830s).
Chiang Kai-shek allied with Du and the Green Gang against the communists and pro-communist unions in Shanghai. The resulting massacre, known as the 1927 Shanghai Purge, ended the First United Front. As a reward for his service, Chiang appointed him to the Board of Opium Suppression Bureau.
Du also supported the Nationalist government with funding. In return, he was allowed to run labor unions and continue with his drug-dealing business. Due to the division in China during the Warlord era, the government of Chiang Kai-shek only nominally controlled most of China, and Chiang had to rely on the local gangs such as that of Du to have any actual and effective control. When the Nationalists declared war on Japan in 1937, Du smuggled supplies from occupied Chinese territory.
The relationship between Chiang and Du soured after World War II. The corruption and crimes committed by Du's associates (including his own relatives) were causing great problems for the Kuomintang. When Chiang Kai-shek's son, Chiang Ching-kuo, launched his anti-corruption campaign in Shanghai in the late 1940s, Du's relatives were among the first to be jailed. Although Du had successfully managed their release by threatening to expose Chiang's own relatives' crimes which were much more serious, the jailing of Du's relatives effectively end the honeymoon between Chiang and Du.
When Chiang's Nationalist government fled to Taiwan in 1949, Du refused to follow the nationalists and escaped to Hong Kong because he still doubted the communists would forgive him for what he did in 1927. After liberation, Du was convinced that it was safe to return to China. However, before he undertook his return trip, Du died in 1951 due to illness.
The movie "Shang-Hai huang di-zhi" was very loosely based on his life.