Abstract: Switch-zoom dual field-of-view long-wave infrade (LWIR) telescopes are widely used in IR system，and they have the advantages of high transmission in narrow field view (FOV) and high resolution in wide FOV. This paper established the configuration of a switch-zoom dual FOV telescope, explained the athermalization theory of the switch-zoom dual FOV telescope, and designed a passively athermalised switch-zoom dual FOV LWIR telescope operating in 7.7 m~10.3 m. Diffractive surface and aspheric surface were used to improve the quality of optical system.The MTF was 0.45 @18 lp/mm at -55℃~+70℃. Finally, 2 other lenses were designed based on the designing result of the switch-zoom dual FOV telescope, which indicated that the configuration and arrangement of the passively athermalised switch-zoom dual FOV telescope are applicale in a variety of designs.