The invention discloses a long-wave infrared continuous-zooming online fast compensation installing and adjusting device and method. The compensation device comprises a reflecting infrared collimator (101), a reflector (102), a black body (103), a calibration target (104), a long-wave infrared continuous-zooming lens (105), an adjusting device (106), a detector (107), a control circuit (108) and a display (109), and the long-wave infrared continuous-zooming lens (105), the adjusting device (106) and the uncooled infrared detector (107) form a relatively independent subsystem. The device solves the problem of defocusing caused by zooming process of the infrared continuous-zooming lens, installing and adjusting efficiency of the high-accuracy continuous-zooming lens is improved, installing and adjusting cost is reduced, and damage risks of the lens caused by repeatedly disassembling and assembling in the assembly and calibration process are avoided.