The invention discloses a signal conversion device for an accelerometer in a strapdown inertial navigation system. An analog current signal output by the accelerometer is converted into an analog voltage signal; the analog voltage signal is subjected to integration by a voltage-to-frequency (V/F) conversion module; one path of analog voltage subjected to integration is output to a pre-amplification circuit, and the other path of analog voltage subjected to integration is converted into a pulse signal and the pulse signal is output to a field programmable gate array (FPGA) processing module; the pre-amplification circuit matches a range of the input analog voltage with an input voltage range of an analog-to-digital (A/D) conversion module; the A/D conversion module converts the analog voltage into a digital value signal and outputs the digital value signal to the FPGA processing module; the FPGA processing module acquires number of pulses output by the V/F conversion module in unit time, the number of the pulses is used as an integer part for calculating the number of pulses, the acquired number of pulses and the digital value signal input by the A/D conversion module are stored in fixed time, and a decimal value of the number of pulses in an acquisition period corresponding to the digital value signal is calculated; and a digital value corresponding to the analog current signal output by the accelerometer is determined according to the integer part and the decimal value of the number of pulses, so that the signal of the accelerometer is converted.