By analyzing Doppler radar data and TRMM PR data of Qinghai-Xizang Plateau in 1998, we compare the difference and similarity of cloud observation by ground based Doppler radar and TRMM PR in many different aspects, such as echo structure, echo intensity and precision of rainfall measuring. Some causes are given to interpret these deviations.Generally, the echo structure observed by TRMM PR is very similar with that observed by ground based Doppler radar, but the echo intensity observed by TRMM PR is greater than that observed by ground based Doppler radar. Echo intensity observed by TRMM PR has systematic deviation of 23 dB with that observed by ground based Doppler radar.Because of the different observational mode and transmittal wavelength of TRMM PR and ground based Doppler radar, the scatter property for those cloud particle of the different phase and spatial direction is also different. Therefore, the deviations of cloud observation is caused.