It's an anti-counterfeiting measure. At one point, Chinese currency had pictures of random and unknown peasants and workers. read more
As for why Chairman Mao's choice is very simple, because people are very familiar with Chairman Mao, even if farmers know that this is a way to quickly identify money. Mao Zedong clothes collar feels and ordinary paper is not the same.The most important reason I think is because the RMB internationalization, Mao Zedong as a picture, easier to identify. read more
The 1990-type note has a portrait of four formerChinese leaders, namely Mao Zedong, Zhou Enlai, Liu Shaoqi and ZhuDe, on its obverse while its reverse is the Jinggangshan Mountain in South China. Very few of the 1990-type 100-yuan paper notes arecurrently circulated in China. read more