The roller-floating bush-pin (RFBP) structure is an important component in high-pressure fuel pumps of marine diesel engines. Considering the thermoelastic effect of the double-layer oil film structure and the time-varying working conditions of the fuel pump, a simulation model for the transient dynamic characteristics of the double-layer oil film structure and a test platform for the double-layer oil film lubrication system were established, verifying the accuracy of the simulation model. Through the comparative analysis of the dynamic parameters of the inner and outer oil films, the influences of working parameters and structural parameters on the dynamic characteristics of the structure were studied. The results show that, compared with the single-layer oil film structure, the double-layer oil film structure can significantly reduce the stiffness and damping of the structure. The dynamic characteristics of the internal oil film show greater sensitivity to changes in operating parameters and structural parameters. The influence of the outer oil film on the equivalent dynamic characteristics of the RFBP structure is more significant than that of the inner oil film. This work can provide useful guidance for the design of roller floating bushing pins in the oil supply mechanism.