Abstract: A mobile X-band phased-array meteorological radar (XPAR) is developed by State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, and Anhui Sun-create Electronics Limited Company. The XPAR scans electronically in elevation while scanning mechanically in azimuth, transmits radar wave with wide beam width (about 20° in vertical direction and 1° in horizontal direction) and receives 14 beams simultaneously. As reflectivity calibration is key technique for the active phased-array radar application in meteorological observation, the testing and calibrating method for the XPAR is investigated according to characteristics of the transmitter/receiver (T/R) the multi-beam work mode. The test and calibration focus on the antennas, T/R, purse compress and the variations of gain and beam width with the angle of the antenna beam in respect to the normal of the array face, in order to reduce the observation bias introduced by different modes. After calibration, the XPAR is used to observe 3-D structures and evolutions of convective precipitation in field experiment at Dingyuan of Anhui Province and Ganzi of Sichuang Province from May to August in 2014. The data of an S-band operational radar (SA) and a C-band polarization radar (CPOL) nearby are used to examine the observation capability of the XPAR. Results show that the antenna gain and its variation with the scanning angle, the beam direction, dynamics ranges of T/R are in conformity with the design. The transmitter and receiving characteristics for 128 T/R are similar. The calibration bias for reflectivity and radial velocity measurement are less than 0.98 dB and 0.1 m·s^-1, respectively. Variations of T/R parameters in observation are watched and corrected by the correcting network. Comparing with the SA and CPOL, the bias of reflectivity in Fine Mode is less than 1 dB, the biases for Guard Mode and Quick Mode are less than 2 dB, and the velocity observed in three modes are accordant very well. The bias of reflectivity and radial velocity by XPAR are reasonable. The horizontal and vertical structures of precipitation observed by 3 radars are similar. And calibration results provide basis for quantitative measurement of the XPAR.