With the development of HVDC technology, the interaction between AC and DC hybrid systems has become the research focus. For AC systems with HVDC system connection, its fault analysis method under asymmetric faults is studied, and the equivalent model of LCC-HVDC composite sequence network on AC side and the calculation method of short-circuit current are proposed. Firstly, the LCC-HVDC switching function model under asymmetric conditions is built. Then, the phasor model of LCC is established based on the switching function model, and the calculation method of LCC Compound sequence network is deduced. Finally, combining the LCC compound sequence network model with the boundary conditions of asymmetric faults in AC system, an iterative algorithm for solving the short-circuit voltage and current of asymmetric faults in AC system with HVDC system access is proposed and verified by simulation. The simulation results show that the proposed fault current algorithm can meet the requirements of Engineering calculation.