The invention relates to a self-adaptive amplifying and filtering system for laser energy measurement of a back calorimeter, which comprises a calorimetric detector, an impedance matching device, a front programmable gain amplifier, a programmable switch capacitance low-pass filter, a post programmable gain amplifier, a signal acquisition and control module and a gain and bandwidth control module, wherein the signal acquisition and control module analyzes and processes an acquired signal by adopting a self-adaptive frequency spectrum analysis method and transmits processing results to the gain and bandwidth control module; and the gain and bandwidth control module downloads the processing results to the front programmable gain amplifier, the post programmable gain amplifier and the programmable switch capacitance low-pass filter. The self-adaptive amplifying and filtering system has the benefits that the gain of all amplifiers and the bandwidth of the filter are realized through online adjustment, the use is convenient, and the signal to noise ratio of an output signal is improved while the environmental noise is effectively restrained.