This question already has an answer here:
I was born in China, immigrated to Canada and obtained Canadian citizenship. I did not renounce my Chinese citizenship. After obtaining my Canadian passport, I went back to China for a while. I later returned to Canada via the US. I have a 10-year US visa on my Chinese passport and I used to it to travel to the US. Then I flew to Canada using my Canadian passport. Therefore, the last record on my Chinese passport is me entering the US. While in Canada, I decided to go study in the UK, so I applied for a student visa using my Canadian passport.
Currently I am in the UK as a Canadian international student and have just completed most of my studies. My dissertation is on the Chinese consumer market, so I am planning to return to China to conduct my research. However, I am very confused as to how I could return to China without the Chinese authorities finding out that I have two passports. Which passport should I use to travel?