In order to reveal the cracking mechanism and the anti-crack performance of infill walls of aseismic structures,and provide information for the performance-based seismic design of infilled structures,the in-plan cracking of masonry infill walls is analyzed by means of finite element method. The results show that the cracking mechanism of the infill walls is very complicated,and that the cracking and anti-crack performance mainly depends on the storey drift angle of the frame and the strength of wall materials. The story drift angles of the masonry infill walls with different elastic moduli are obtained in different cracking widths. The result can be applied to the performance-based seismic design of infilled frame structures.