A new type of spectrosensitometer has been developed, which is characterized by a wide spectrum range of 340 nm ~ 900 nm and a large exposed area of 202 mm × 90.5 mm with multi-step light intensities on it. The optical density value error of each step on the 18-step wedge with high precision is not greater than 0.01. The film filter evaporated according to the spectral characteristic of the light source can eliminate the secondary spectrum of grating. The automatic control acquisition system is developed by LabVIEW and all-in-one PLC with HMI. In the horizontal direction, the grating displacement sensor is adopted to form the closed-loop control, and the wavelength positioning deviation is less than 0.05 nm. Linear compensation method is adopted in the vertical direction with a height deviation of less than 0.05 mm. The spectrosensitometer automatically measures the optical power per unit area of lights with different wavelengths and light intensities on the step wedge. The shutter controls exposure time. Photosensitive materials are once exposed within the scope of the wide spectrum. After being developed and fixed, the optical density value can be measured by densitometer. The spectral sensitivity curve of a photosensitive material with a certain optical density value can be drawn according to the national standard (GB10557-89).