The invention discloses a method and a device for implementing a Ramsey-CPT atomic clock by microwave On-Off modulation VCSEL. The method comprises the following steps of: A, coupling direct current and microwave to a laser tube, scanning the direct current to obtain a plurality of absorption peaks and locking the direct current; B, switching on and off the microwave to realize equivalent laser pulse, and scanning the microwave to obtain Ramsey-CPT stripes; and C, locking the microwave to obtain stable frequency output. The device is characterized in that: a current source is connected with a Bias-Tee, a microwave source is connected with the Bias-Tee through a microwave switch, the Bias-Tee is connected to a laser generating device, the output laser passes through a physical system and then enters a laser detection device, and control equipment is connected with the current source, the microwave source, the microwave switch and the laser detection device respectively. The method and the device realize laser-atom periodic interaction through microwave On-Off, have a more predominant frequency discrimination curve compared with the traditional CPT scheme, and implements the atomic block with higher stability. Compared with the Ramsey-CPT atomic clock implemented by using the AOM with larger volume and higher power consumption, the device has a simple structure, adopts a unique method, is easy for microminiaturization, and overcomes the key technology of the chip Ramsey-CPT atomic clock.