A projection system, a display system and monitoring methods thereof are provided. The projection system includes at least one projection device, at least one sensing device and a remote device. The at least one projection device is coupled to the at least one sensing device. The at least one sensing device senses a plurality of environmental parameters and a plurality of device output values on the at least one projection device. The remote device receives the environmental parameters and the device output values to execute state analysis for the at least one projection device, so as to generate at least one analysis result. The remote device further generates a command signal according to the at least one analysis result, and transmits the command signal to the at least one projection device. The at least one projection device executes a self-protection procedure according to the command signal.