The transient model of a trough concentrating solar Photovoltaic/ Thermal system based on GaAs cell array has been established. The annual performance of TCPV/T system by south-north horizontal tracking mode has been analyzed with the transient model and TRNSYS software. The results indicate that the thermal and electrical energy per year increase linearly with the optical efficiency of mirror, also increase at first and then tend to be steady with increasing of the thermal conductivity of heat sinking tape. But with increasing of the insulation thickness, the thermal and electrical energy per year increase firstly and then decrease. The optimal U-value of heat sinking tape and the optimal insulation thickness are 1000 W·m⁻²·k⁻¹ and 1.0 cm respectively. However, the optical efficiency of mirror should be improved effectively for enhancing system performance. All those works benefit to further study on optimizing system design.