The pipe fluid-heat coupling heat transfer calculation and the analysis of structural deformation under thermal boundary conditions were conducted based on the standard flame simulation. In addition, the influence of the flammable liquid pipe fitting material and structure parameters on the pipe fitting contact stress was calculated and analyzed in the standard flame scenario. The calculation results indicate that, in a standard flame scenario, while the tensile modulus is smaller, the thermal expansion coefficient is smaller, and the tensile strength of the material is increased, the contact reliability and condition of the pipe fitting would be better. Compared with the 37° sphere-to-cone pipe fitting, the 24° sphere-to-cone pipe fitting has a larger normal contact stress and a smaller contact stress deflection coefficient. While the contact state of the pipe fitting can be improved by using a long pipe clamping distance and small radial size of the fitting. Also, when the axial pre-tightening force of the pipe fitting is larger and the pipe medium pressure is smaller, the contact stress of the pipe fitting is optimized. These results researched in this paper are expected to offer theoretical evidence and support for the fire protection design of engine pipe fitting.