The present invention relates to a wireless communication system and a wake up method thereof. The wake up method includes the following steps: when main equipment has a communication requirement, the main equipment converts a pseudo random sequence code into a wake up bit stream through coding transformation, modulates the wake up bit stream into a wireless modulation signal, and sends the wireless modulation signal to at least one slave equipment in a preset duration time, wherein the preset time is greater than or equal to a sum of a dormancy period and a detection period of the slave equipment; each slave equipment receives the wireless modulation signal in the detection period, demodulates the wireless modulation signal into the wake up bit stream, carries out sampling and decoding on the wake up bit stream, and determines whether to wake up the slave equipment or not according to a decoding result. Through the implementation of a technical scheme of the invention, time synchronization of a wireless communication device involving communication does not needed; anti-interference ability is strong, problems of identity identification and false wake up are solved, and reliability is raised; the detection period of the salve equipment can be shortened, a receiving window time of the salve equipment is reduced, and power consumption of a communication system is reduced.