Based on the 4-channel road simulation bench, a scheme of fatigue bench test which was suitable for cab with frame and suspension was designed with the method of multi-body dynamics simulation and physical iteration. Large load and large displacement signals above the suspension can be loaded on the test bench, and it is effective for the fatigue bench test of the same type. The multi-body dynamics model was built according to the durability specifications of cab assembly, and the feasibility of the scheme was proved through the verification for the fixture and virtual iteration analysis. The test bench with linear guide and spherical joint was built to simulate the actual condition of cab on suspension based on the results of the road load signal analysis and multi-body dynamics analysis. The acceleration signal beside the suspension was taken as a target signal and the drive signal of cylinders was obtained through physical iteration. By comparing three different iterative result of test scheme, the linear guide installed on the back of cab and the spherical joint installed on the bottom of front cylinder is the best scheme. The iterations on 11 different roads were realized and the RMS error of target signal was substantially less than 13%.The iteration results agree the test requirement well, and the results of fatigue bench test agreed well with proving ground test in terms of the damage distribution. The secondary development for 4-channel road simulation bench is not only efficient and accurate to assess the durability performance of the cab assembly with suspension, but also provides a guiding significance for the functional diversification development of the test bench.