Structural analysis, especially the thickness effect on the structural strength, of a bileaflet mechanical heart valve prosthesis with curved leaflets is presented in this paper. Taking the wide variations of the blood flow pressure on the leaflet surface, the structural stresses inside the leaflet and deflections of the leaflet are investigated by adopting both linear and nonlinear structural analysis techniques for more accurate results comparison. The thickness of the curved leaflet also varies considerably from 0.50 mm to 0.75 mm by 0.05 mm. These are very useful for the design of the mechanical heart valve (MHV) prosthesis. Linear and nonlinear structural mechanic analyses for the leaflet of the MHV prosthesis are conducted to predict the structural strength variation of the leaflet as the leaflet thickness changes. Analysis results show that the structural strength of the leaflet decreases as the leaflet thickness becomes thinner and thinner, and the nonlinear structural behaviors of thin leaflets are very conspicuous for large applied blood pressures. Hence, these thin leaflets are not desirable for the in vivo use of the MHV prosthesis.