The present invention discloses an automatic regulating device and method for intermediate frequency in wide frequency band of a signal source analyzer, and belongs to the technical field of electronic testing. According to the method, two-stage gain-controlled gain adjustment models are constructed, one is a 5dB large step gain adjustment model for rough gain adjustment, and the other is a 0.25dBsmall step gain adjustment model for fine gain adjustment. Frequency response of channels of signals is corrected according to two dimensions of frequency and amplitude of 10MHz-67MHz wide frequencyband signals, according to magnitude of power of the radio-frequency signals, after DC bias search is performed, the two-stage gain-controlled gain adjustment models are adjusted in real time, and automatic adjustment of intermediate frequency gains is achieved. According to the method, magnitudes of the intermediate frequency signals can be ensured to be adjusted within a maximum dynamic range ofADC signal acquisition under the unsaturated conditions, and phase noise measuring sensitivity is improved.