Based on the perception records on cold/warm in Weng Tonghe Diary and the contemporary monthly average instrumental temperatures in Beijing and Shanghai. The correlation between the perception records on cold/warm and temperature variation is investigated with correlation analysis and regression analysis. The result shows that they are significantly correlated. It means that the  monthly days of colder （CD）, extremely cold （EC）, hotter （HT）, and extremely hot （EH） could be used as a proxy index to indicate the past temperature change. However, the validity of the proxy index is various on the time scale of climate change and the season. Firstly, the monthly days of EH, HT, CD, EC could represent the monthquarter variation of temperature change, with CD and EC being the best. Secondly, on the time scale of interannual, the perception days on cold/warm can not represent the temperature variation for the summer months （Jun., Jul. and Aug.）, the monthly days of EC are the best proxy indexes for Jan., Mar., May, Sep. and Dec.. Besides, the monthly days of EC can also be used to identify the extremely cold/warm year. Thus, it can be concluded that the perception records on cold/warm in historical private diaries can be used to study climate changes of historical period.