Firstly, the generation mechanism and characteristics of zero-sequence inrush current are analyzed. Secondly, a new zero-sequence overcurrent protection scheme based on second harmonic compound blocking is proposed to solve the problem that zero sequence overcurrent protection will malfunction. By comparing the second harmonic content of zero sequence current and its change rate, the new method can identify short circuit current and inrush current, which can be unaffected by CT saturation. This paper designs a counting device to monitor the change rate of the secondary harmonic and gives the corresponding principles of setting and counting. Combined with zero sequence overcurrent protection setting current and action time, a new zero sequence overcurrent protection scheme is proposed, which is simple, clear and easy to implement. In addition, it has a certain engineering application foundation. This paper verifies the effectiveness of the new scheme in different scenarios by building a 220 kV system model in PSCAD/EMTDC. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52170218000M) “Research on Hybrid Multi-DC Transmission Line Fault and Self-adaptive Reclosing Method”.