Abstract: The underwater acoustic channel is complicated，and the transmission of weak acoustic signals is often interfered by other signals.In order to obtain a higher signal-to-noise ratio，the acoustic signals received by hydrophones are usually filtered.Based on the FPGA hardware platform，using the FIR filtering algorithm and through the self-parsing algorithm of filter parameters to achieve precise control of the cut-off frequency and steep transition band，a broadband programmable filter for underwater acoustic metrology is designed.The cut-off frequency is adjustable from 1 Hz to 1.59 MHz，and it can be configured as high-pass，low-pass，band-pass，or band-stop.The out-of-band attenuation is greater than 48 dB/Octave.The parameters of the metrology-grade programmable filter can be configured via RS232，GPIB，or LAN.The results of design simulation and application test show that the programmable filter can be applied to various underwater metering scenarios with different filtering requirements.The parameters are flexible and changeable，and the real-time performance is strong，which can meet the needs of underwater acoustic metering.

Key words: Digital filter, Automatic test system, Finite impulse response, Field-programmable gate array