When measuring the laser beam parameter, in order to solve the problem of different laser wavelengths have different focal positions for focusing optical system, simplify the measurement procedure and reduce the measurement error, the superachromatic focusing optical system for wide spectrum is designed. Based on the theory of wavefront chromatic aberration, the equations for the initial structure of the superachromatic system are derived. The superachromatic system is designed by the optical design software ZEMAX. It′s waveband is 350~1100 nm, the focal length is 250mm and the entrance pupil diameter is 25 mm. The longitudinal aberration and the focal shift curve of design results are given. Analysis shows that the spherical aberration curves of different wavelengths at 0.707 aperture intersect at one point approximately, which achieve the superachromatic. The focal shift in the working waveband is only 38.2 μm, and the focal plane position is fixed basically, which meets the measurement requirement of laser beam parameter from ultraviolet to near infrared.