A spectral imaging module was added into a laser scanning confocal microscopic system to discriminate different fluorescence components in biological tissures. A prism was used as a beam split part, and two movable slit edges were used to form a slit whose width and position could both be adjusted on the spectral image plane. The two slit edges were installed on a stepping motor. By adjusting two slit edges, the laser scanning confocal spectral microscopy could work at wavelengths of 400-700 nm and its minimum spectral wavelength for confocal imaging was less than 5 nm. The actual slit positions corresponding to spectral lines of 488 nm laser and low pressure mercury lamp were tested and compared with the theory positions. The results show that the differences of the actual slit positions and theory values are all less than 0.1 mm. A laser scanning confocal imaging experiment with a full spectrum confocal imaging and 2.5 nm spectrum bandwidth (50 μm slit width) confocal imaging was carried out using a mouse kidney tissue slide. The images of nuclei labeled by DAPI and glomeruli labeled by Alexa Fluor 488 were obtained and the different components in biological tissues were distinguished. It concludes that the system can complete the confocal spectrum imaging, by which the application area of laser scanning confocal microscopy has been extended.