Talus deposit is often seen in the hydropower projects in the southwest of China. Its mechanical properties are so complex that microscopic structure study is often used to reveal the essence of deformation and damage. The digital image processing technology (DIPT) is introduced to the discrete element simulation of talus deposits. Based on the study of DIPT, a Photo-To-PFC (PTP) automodeling program is developed. It is able to realize the whole process: analyzing and processing the digital image, acquiring the information and establishing the model files. The discrete element model of talus deposit can be established fast and correctly by the PTP from the digital photo on-site. A new way is opened up for the study of the talus deposit. As an example, some talus deposit data of Gushui hydropower station is used, structure model and mechanical properties of talus deposit are studied based on DIPT and PTP. The mechanical properties are studied by the numerical simulation of biaxial compression test. The results show that the gravels and soil mass compress with each other to form a corporate load-carrying body for sharing the external forces. The stress-strain curves show a strain-hardening stage obviously due to the impact of gravels. With the increasing of bond strength among soil particles, the initial elastic modulus and peak strength of talus deposit go up at a certain level; the initial elastic modulus and peak strength increase a lot as the existence of gravels.