Cheng was born in Hangzhou, Zhejiang Province in 1899 in the late Qing Dynasty.

[3] Liang wrote that Cheng engaged in "obsequious flattery" of Adolf Hitler in an attempt to win his favor, and his dispatches to Nanking showed a very shallow understanding of National Socialism.

[3] By 1936, many of the Chinese diplomats in Europe had come to favor the idea of collective security under the banner of the League of Nations as the best way to rally support from the great powers as China faced increasing aggressive Japanese claims that China was part of the Japanese sphere of influence.

[3] Germany was the largest supplier of arms to China while a German military mission was training the National Revolutionary Army, and Cheng's warnings that a League-based foreign policy would strain Sino-German relations carried much weight with Chiang Kai-shek.

The other Chinese diplomats felt that Cheng was too weak a figure to oppose General Hiroshi Ōshima, the Japanese military attaché in Berlin, who was a great friend of Joachim von Ribbentrop.

[4] These concerns were increased when Hitler on 4 February 1938 fired Baron Konstantin von Neurath as Foreign Minister and replaced him with Ribbentrop, thereby placing German foreign policy in the hands of a man who was well known for favoring Japan over China.

[3] In his last message to the Chinese government, which had forced to relocate to Chongqing, Cheng predicated that Europe was on the brink of war with Germany threatening to invade Czechoslovakia.