Influences of rain shield for GL—5000P radiosonde humidity sensor on humidity measurements is researched by using computational fluid dynamics（ CFD） method. The humidity measurement system structure is modeling by Pro / E software

and it is meshed with ICEM pre-processing software. Fluent software is introduced for steady-state and transient calculation and analysis. The simulation results show that the rain shield effectively prevents the effects of high-altitude clouds and rain on humidity sensor; rain shield combines certain features of anti-solar radiation

but its ability of anti-solar radiation is significantly weakened at high altitude（ over 25 km）

and even it plays the opposite role; thickness of rain shield has less impact on solar radiation error

however

impact of its reflectance seems more significant; transient analysis reveals that humidity field distribution of sensor surface produces time lag

and time lag constant increases with increasing altitude

and it reaches 0. 42 s at 27 km.This research provides theoretical basis for time lag correction of humidity vertical profiles.