for 640 pixel×512 pixel cooled staring focal plane array detector, a visswir wideband continuous zoom optical system with 7x zoom range is presented based on the pattern of the negative zoom group and compensating lens group. the zoom system provides continuous changed in the field of view from narrow to the wide. the zoom optical system works in the range of 0.4μm∼1.7μm, f number is 4, the pixel of the detector is 15μm. it realizes 20mm∼140mm continuous zoom with a smooth zoom path and provided high image quality with the whole zoom range, the zoom ratio is 7:1. the modulation transfer function(mtf) for the system is above 0.5 within the whole focal length range at spatial frequency of 34lp/mm and it almost approaches the diffraction limit. rms value of spot diameter was investigation, the maximum distortion value is less than 5% and the surface type of all lens applied is spherical. moreover, the cam curve after optimization is given by the optical design software code v macro. the design results provide that the zoom system has the small size, high resolution, excellent image quality and the smooth cam curve etc. © 2017 spie.