In order to suppress over current and over voltage in the recovery process when the rectifier side occurred fault in the HVDC transmission system, the rectifier side minimum firing angle control is researched based on the DSP, which is developed by the Electric Power Research Institute of CSG. By selecting the power components signal as the input signal, through the reasonable control logic and the appropriate parameters adjustment, a custom block which can achieve the minimum firing angle control function is designed. On the basis, A detailed comparison of the 10 variables in DSP (minimum firing angle control) model and DSP (no minimum firing angle control) model and PSCAD (without adding any control) model is made, The simulation results show that the designed custom block can achieve the purpose of suppressing over current and over voltage when the rectifier side occurred fault. This has certain reference significance to the actual HVDC transmission control system.