The factors that affect observation height of wind profiler radars are analyzed according to weather radar equation. In addition, the mathematical model for the effect of array unflatness on antenna radiation pattern of wind profiler radars is established. The variations of antenna gain and side lobe level with array unflatness for vertical pointing beam and 15° offzenith beam are simulated. Simulation results show that antenna gain of wind profiler radar reduces approximately in exponential as array unflatness increases, and the overall antenna sidelobe level goes up with increased array unflatness. Therefore, it is suggested that in the acceptable degradation for observation height of wind profiler radar, considering domestic antenna structure design, manufacturing level and mounting accuracy, engineers can put forward reasonable technical specifications on array unflatness.