The structure and operating principle of an air-charged split-type adjustable shock absorber was described, a non-linear parameterized mathematical model of this shock absorber's damping characteristics was established according to fluid mechanics theory and the main structural affection factors to shock absorber's damping performance, such as the diameter of piston valve orifice, the diameter of adjustable orifice, the initial volume of gas chamber, the diameter of piston rod, the inner diameter of oil pipe and so on, were analyzed by simulations. The damping performance and damping force adjusting scope of a shock absorber specimen was tested, the testing results proved the validity of simulation results and the mathematical model of shock absorber.