The invention discloses an adaptive adjustment device for a power supply of a logging instrument power amplifier. The effective value of the amplitude of an emitted signal is converted into a direct-current voltage by detecting the amplitude of the emitted signal in real time, sampling is carried out through an 8-bit parallel port ADC sampling module, parallel port output is achieved after analog-digital conversion, and the analog quantity of the amplitude of the emitted signal is converted into an 8-bit binary digital quantity and then reflected as the output voltage value of the switching power supply. Non-linear errors of the switching power supply and power amplifier output are removed through reasonable circuit parameter matching, so that the change of the emitted signal has a linear direct proportion relation with the input voltage of the power amplifier, namely, the output voltage of the switching power supply, the power amplifier works in a nearly full-load output state all the time, the heat loss of the power supply is reduced, the efficiency of the power amplifier is improved, and the system power consumption is reduced. Meanwhile, in the device, whether the switching power supply or a system main power supply is used for supplying power can be automatically selected for the power amplifier according to the amplitude of the emitted signal.