On the basis of average temperature from 78 meteorological stations in the Yellow River basin, the monotonic trends of temperature over the past more than 30 years are analyzed with linear trend method and Mann-Kendall method. The analysis is mainly made for 12 months and the annual average temperature with the emphasis on the result of Mann-Kendall method. The isogram for the long-term trend of annual temperature is given. The result shows that the average temperature exhibits an increasing trend, mainly because of the increase of temperature in December, January and February. The largest trend is shown in December, while the smallest in August. However, temperature from several stations and months show declining tendency. Large differences show in areas and months, and according to these differences, the Yellow River basin is further divided into four regions.