Abstract: A large number of simulation analyses for the column-bracing systems with different distributions of the initial imperfections have been conducted by the ANSYS program, in which random combination of the initial imperfections between columns and braces is considered by the Monte Carlo method. According to the analysis results, four kinds of buckling modes of column-bracing system have been found, probability density function of the bracing force are proposed through probability statistics, and the design bracing forces are also obtained. The results indicate that the random combination of the initial imperfections between columns and bracing bars leads to the randomness of the bracing bars in compression or in tension, so that the design bracing force can be reduced. The above design bracing force is much smaller than that proposed by the “Code for design of steel structures” (GB 50017).