The invention discloses a polarization multiplexing-based direct detection wind lidar. based on the principle that laser beams having mutually perpendicular polarization states have different transmittance curves when passing a Fabry-Perot interferometer, a continuous laser beam is divided into two branches having the mutually perpendicular polarization states by the polarization multiplexing technique, one branch is used to detect the atmospheric wind field after subjected to pulse modulation, the other branch is used to lock laser frequency, the two branches share the Fabry-Perot interferometer, and the two branches are combined, separated and detected with a polarization-maintaining combiner and a polarization splitter. The use of one Fabry-Perot interferometer allows frequency shift detection and frequency tracking and locking to be simultaneous; compared with the system comprising a multi-channel Fabry-Perot interferometer or multiple Fabry-Perot interferometers, the lidar has lower cost, compacter structure and higher stability.