A two-piece optical prism includes a prism having a groove and prism having arc faces, where the prism having a groove has at least one first arc face and groove having at least one second arc face, and the prism having arc faces is placed in the groove of the prism having a groove and has at least one third arc face. The present invention can be used in the surface plasmon resonance optical system for the angle, range adjustment and control of incident light (e.g. laser light), capable of constituting an optical wide-angle, multi-angle incident system to carry out the wide-angle, multi-angle scanning detection of surface plasmon resonance, increasing the system dynamic detection range and sensitivity; and further reducing a detection chip.