A frequency modulation-frequency shift keying (FM/FSK) demodulator is provided, including a modulation signal input terminal for receiving a first modulation signal; a phase shifter for receiving the first modulation signal and then shifting its phase to output a second modulation signal; a multiplier connected to the modulation signal input terminal and the output of the phase shifter for multiplying the first modulation signal and the second modulation signal together to output a demodulation signal; an adder having at least two input terminals and an output terminal where the first input terminal receives the demodulation signal; a direct current (DC) compensation unit connected to the output terminal of the adder for compensating the DC of the demodulation signal and low-frequency offsets, and a demodulation signal output terminal connected to the output of the adder for outputting the demodulation signal.