In this paper, a phase demodulator based on surface acoustic wave (SAW) delay line is proposed. The basic idea is to demodulate a phase-modulated signal using the "delay addition" method after converting it to an amplitude-modulated (ASK) signal using a SAW delay line. The delay line achieves a delay time of 1 μs in the frequency range of 2.695 GHz to 3.00 GHz, and the proposed demodulator can demodulate BPSK-modulated signals with modulation rates of 500 kHz and 1 MHz.