An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as afrequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS, GLONASS, Galileo and Compass. Our research group, the Atomic Clock and Precision Measurement (ACPM), concentrates on the research of microwave frequency standards and precise measurement, including Rubidium atomic clock, compact Cesium beam clock and Optically Pumped Cesium Magnetometer.