Inspired by dense trajectory feature,an action description algorithm based on depth motion trajectory information is proposed in this paper .Firstly,according to dednse optical flow field,dense interest points and dense trajectories f or L frames depth videos are extracted.Secondly,the depth information of front and back interest points in the same trajectory is exploited to compute the change values of depth which are added into dense trajectory and the computing method of histogram of oriented gradient (HOG) descriptor.Thirdly,average change value of depth which is used to judge t he change status of depth information for all actions in entire dataset is calculated.Finally,based on t he change status of depth information,distinctive codebooks are chosen to make projection and classificat ion for video sample.The experimental results on two public datasets of DHA-17and UTKinect show that th e action description algorithm based on the depth motion trajectory information has desirable distinctiveness a nd robustness,and the performance is comparable with that of some advanced and r epresentative algorithms.