The present invention discloses an echo detection optical system. The echo detection optical system includes a laser light source, a through-hole reflector, a reflection prism and a light receiving system; a laser beam emitted from the laser light source passes through the through hole of the through-hole reflector and is reflected by the reflection prism; the reflected laser beam irradiates a target detection space; when the laser beam irradiates a detection target in the target detection space, the echoes of the detection target are sequentially reflected by the reflection prism and the through-hole reflector; and the reflected echoes irradiate the light receiving system. The echo detection optical system has the advantages of simplified structure, reduced size and decreased costs.