Abstract: Based on the temperature observations at 699 national base stations from 1961 to 2002, analysis is performed of the difference between average temperatures by means of different methods. The result shows that due to different calculating methods with 4 observations and 3 observations on a daily basis, certain difference arises in averaging 4 and 3 observations. This difference is remarkable in spatial distribution. The 3 observations averaging is higher in the west and north, but low in the southeast. There is an increasing tendency in the difference for the central and western part, owing to the rise of minimum temperature. As a result, in using mean temperatures attention should be paid to the methods to avoid errors then the average of temperature is applied in study.