Impact parameter errors existed in the test organization. In order to understand sensitivity of vehicle acceleration versus to impact parameters, finite element simulation model of a vehicle impact to a combined barrier was set up and sensitivity analysis was done after finite element model proved to be correct by impact test. The results indicate that the simulation method is reliable since the results of simulation match to that of crash test, the sensitivity coefficients of body acceleration versus to vehicle quality, to impact angle and to impact velocity are -0.58, 1.63 and 4.18, the impact speed is the most sensitive factors to vehicle acceleration. The research results have guidance significance to set out error range of barrier impact test.