Abstract: The calibration methods of superconducting transducers with alternative magnetic fields were established.Different ways of construction software gradiometers and their performances for environmental noise cancellation were studied.Sensor calibrating with different frequencies and amplitudes showed good consistency.The constructed synthetic first order gradiometers demonstrated good ability for environmental noise rejection,enabling detecting of weak magnetic field of 50pT in normal urban laboratory environment.The uncertainty of the calibration and the observed minor differences between different gradiometers were also discussed.