Abstract: A heterodyne interferometer and a measurement method based on multi-target opposite displacement measurement are provided, technical points including: An output path of the laser source is sequentially arranged with a first beam splitter and a second beam splitter arranged in parallel on left and right sides, and both of which are polarization beam splitters; a first reflector is arranged above the first beam splitter, a third reflector is arranged on a right side of the second beam splitter, a second plane reflector is arranged in front of the second beam splitter, and a first plane reflector is arranged behind the second beam splitter; the first plane reflector and the second plane reflector jointly constitute a second reflector group; a left side of the first beam splitter is provided with a first photodetector and a second photodetector. The present invention realizes the measurement of relative displacement between opposing objects.