A calibration system and a calibration method for a phased-array antenna are provided. The calibration system includes a receiving probe, a parameter tester, an upper computer and a beam controller. The receiving probe may acquire a beam signal, which is radiated by a to-be-tested phased-array antenna according to a provided microwave signal, at a preset position. The parameter tester may generate a test parameter according to the microwave signal and the beam signal. The upper computer may determine whether the to-be-tested phased-array antenna meets a preset index according to the test parameter, and in a case where the to-be-tested phased-array antenna does not meet the preset index, calculate the test parameter according to a genetic algorithm to generate optimized beam control data. The beam controller may generate a control voltage according to the optimized beam control data, and transmit the control voltage to the to-be-tested phased-array antenna.