The invention relates to a soft start method for a physical detection transmitter, comprising the following steps: before the CUP of the physical detection transmitter sends a dominant waveform, soft start time is increased by 10-70 seconds; during the soft start, the transmitter sends an alternating signal with a gradually increasing duty ratio and a frequency of 100 Hz-500 Hz; the current control capability of IGBT is utilized to increase output power gradually. By utilizing the start method of the invention, destructive impact of the sudden and great power change on the working machinery generated by the switch between the two status of operation/standby of the physical detection transmitter can be weakened, the vibration during start can be eliminated, the service life of a generator can be prolonged and unfavorable effects on an electric network can be alleviated.