A set of 8～12 μm infrared (IR) hybrid refractive-diffractive continuous zoom lenses is designed,based on long-wave 320×240 element uncooled thermal IR focal plane arrays (FPA) detector. The continuous zoom system has a large relative aperture,the F# is 1.3, and the zoom ratio is 8. Ge and ZnS are used in the continuous zoom system. A diffractive surface and an aspheric surface are used for correcting the system color aberration and off axis aberration. The modulation transfer function (MTF) is above 0.5 in all focal distance at the spatial frequency of 18 lp/mm, and the MTF approaches the diffraction limit. The energy permeance ratio is greater than 78% when the system receiving radius in the detection sensor is smaller than 17.5 μm, which shows that the imaging quality of the continuous zoom system is very good.