In this paper,a mathematical model for topology optimization of truss structures withconstraints of displacement and system reliability under multiple loading cases is constructed.In orderto avoid the difficulty of computing the structure’s system reliability,a solving approach is presented inwhich the failure probability of system is divided into the sum of all bars’ failure probability by meansof reliability distribution.In addition,by drawing into the reliability safety factor and the fundamen-tal relationship in structural mechanics,all probability constraints of displacement and stress are equiv-alently displayed as conventional form and linear function of the design variables.The optimizationproblem with multiple constraints is treated by the compact constraint tactics and is solved by the im-proved simplex method.The examples show that the approach proposed in this paper is feasible and ef-ficient. In this paper, a mathematical model for topology optimization of truss structures withconstraints of displacement and system reliability under multiple loading cases is constructed.In orderto avoid the difficulty of computing the structure’s system reliability, a solving approach is presented inwhich the failure probability of system is divided into the sum of all bars’ failure probability by meansof reliability distribution. In addition, by drawing into the reliability safety factor and the fundamen-tal relationship in structural mechanics, all probability constraints of displacement and stress are equiv-alently displayed as conventional form and linear function of the design variables. optimization problem with multiple constraints is treated by the compact constraint tactics and is solved by the im-proved simplex method. examples show that the approach proposed in this paper is feasible and ef-ficient.