The invention discloses detection device and method for a high-power semiconductor laser. The device comprises a test bar, a test bar fixing clamp, a condenser lens, a light guide optical fiber and a detector; the test bar is formed by gluing oblique sections of two transparent material bars with the same structure in an opposite and coaxial way, wherein one end of each transparent material bar has a 45 degree oblique section and is plated with a high reflective film specific to the wavelength of a laser diode, and the other end of each transparent material bar has a regular round section; the test bar is arranged on the test bar fixing clamp; the condenser lens is arranged outside one end or two ends of the test bar; and one end of the light guide optical fiber is positioned at the focusof the condenser lens and the other end is connected with the input end of the detector. The invention is applicable to the measurement of high-power semiconductor laser modules of semi-circle shapedor circle shaped packaging structures and has the advantages of simple structure and convenient test operation.