As an important autumn feature, scenes with large numbers of falling leaves are common in movies and games. However, it is a challenge for computer graphics to simulate such scenes in an authentic and efficient manner. This paper proposes a GPU based approach for simulating the falling motion of many leaves in real time. Firstly, we use a motion-synthesis based method to analyze the falling motion of the leaves, which enables us to describe complex falling trajectories using low-dimensional features. Secondly, we transmit a primitive-motion trajectory dataset together with the low-dimensional features of the falling leaves to video memory, allowing us to execute the appropriate calculations on the GPU.