Channel estimation plays an important role in wireless OFDM systems. This paper studies the channel order estimation problem, which aims to estimate the number of paths of wireless channels. We first introduce the traditional channel order estimation method based on minimum description length (MDL) criterion. We find that the traditional method do not perform well when the number of channel samples is small. In order to solve this problem, we propose an improved channel order estimation method, which is also based on MDL criterion. Simulation results show that the improved method has a better performance than the traditional method in terms of estimation precision.