In order to further improve the color display capability of the display system and solve the problem of model incompatibility between the three-primary display system and the multi-primary display system, the method of parameter inequality was adopted for theoretical analysis. Based on the difference between the multi-primary display system and the three-primary display system, the solution space corresponding to the peak luminances of the multi-primary display system was solved. The peak luminances of primaries in a multi-primary display system were deduced theoretically, and the equivalence and completeness of solution space were verified by simulation experiments. The results show that the theoretical maximum gamut volumes corresponding to the simulated four-primary, five-primary, and six-primary laser display systems are 2185100, 2258400, and 2395800, respectively. This scheme has important guiding significance to the theoretical simulation of a multi-primary display system.