This paper focused on applying progressive collapse (PC) procedures on a diagrid system structure and performing an optimization process to find the optimum angle to mitigate the PC with consuming minimum steel weight. Robustness, structural integrity and design of structures against extreme events became utmost necessity. This growing concern of PC was after Ronan Point Apartment Tower collapse in 1968, also Murrah Federal building bombing in 1995 and in 2001 attack on the World Trade Center. The study is performed by analyzing 36, 48, and 60-storey diagrid systems with different inclination angles, 50.2º, 67.4º, 74.5º, and 82.1º, with 2, 4, 6, and 12-storey modules, respectively. This study relied upon the sudden load-bearing element loss technique using the alternative load pass method described by the UFC09 code, by using ETABS software. The analysis results show that the optimum inclination angles range between 75° to 82°.