The wireless communication systems based on Unmanned Aerial Vehicles (UAVs) have found a wide range of applications recently.In this paper,we propose a new three-dimensional (3D) non-stationary multiple-input multiple-output (MIMO) channel model for the communication links between the UAV and mobile terminal (MT).The new model originates the traditional geometry-based stochastic models (GBSMs) but considers the non-stationary propagation environment due to the rapid movements of the UAV,MT,and clusters.Meanwhile,the upgrade time evolving algorithms of time-variant channel parameters,i.e.,the path number based on birth-death processes of clusters,path delays,path powers,and angles of arrival and departure,are developed and optimized.In addition,the statistical properties of proposed GBSM including autocorrelation function (ACF),cross-correlation function (CCF),and Doppler power spectrum density (DPSD) are investigated and analyzed.Simulation results demonstrate that our proposed model provides a good agreement on the statistical properties with the corresponding derived theoretical ones,which indicates its usefulness for the performance evaluation and validation of the UAV based communication systems.