Abstract: When a certain engineering vehicle roll in the sloped area, the impact of the cab interior structure against operator's head will probably cause a serious hurt. As a result, the research on the mechanical response characters of operator's head in the collision accidents was practically significant. In this paper, 3-D finite element modeling technology was adopted to develop the adult headform. The headform was used to analyze the impact on the cab interior structure with virtual test method, and the effect of different densities and thickness of the polyurethane foam on the head injury evaluation criteria was compared. The result showed that the polyurethane foam of 18mm thickness in the cab interior could effectively decrease the head injury value in the secondary collision when the operator was involved in engineering vehicle roll-over. The HIC(d) value decreases as an increase of the foam thickness, and the effect of the foam density variable is nonlinear, a second order parabolic shape can be identified.