The wind field data in near space is of great significance to the attitude control and flight safety for aircrafts. As for the principle prototype of a direct detection Doppler wind lidar (DWL) developed by Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, which can be mounted on aircrafts in near space, its working principle and system structure are introduced, and its relevant technical parameters are given. The DWL principle prototype is self-tested on the ground and the inversion results are compared with those from the coherent Doppler lidar (CDL) and the sounding balloons. The results show that the wind speed and wind direction measurement results retrieved by the DWL principle prototype agree well with those measured by the CDL and the sounding balloons near the ground. Within the height range of 0.3--1.1 km, the root mean square error (RMSE) of wind speed retrieved by the DWL principle prototype is 1.38 m·s -1, and the RMSE of wind direction is 9° based on the CDL measurement results. Within the height range of 0--3 km, the RMSE of wind speed retrieved by the DWL principle prototype is not more than 2.1 m·s -1, and the RMSE of wind direction is not more than 10° based on the sounding balloon measurement results.