To satisfy the projection demand of cinemas with different size, based on mechanical compensation theory, a digital cinema projection lens is designed, and the cam curve is provided. The lens consists of four groups of nine glass lenses, and all the lens surface is spherical. Through comparing with the classical projection zoom lens, the character of the lens designed in the article is introduced clearly. Focal length is 26~28.3 mm, the relative aperture is 1/1.7, the total length is 158 mm, and the caliber is 71 mm. Distortion is less than 2%, at the frequency of 44.6 lp/mm, the axile MTF is higher than 0.68, the meridian MTF of the largest field is higher than 0.38, and the saggital MTF of the largest field is high than 0.58. The design results show that this lens has the merits of high brightness, steady image surface, compact structure and easy to process.