The solar energy flux distribution on the outer wall of the inner absorber tube of parabolic solar collector receiver is calculated successfully by a homemade code adopting Monte Carlo Ray-Trace Method (MCRT Method). It is revealed that the non-uniformity of the solar energy flux distribution is very large. Three-dimensional numerical simulation of coupled heat transfer characteristics in the receiver tube is calculated and analyzed by combining the MCRT Method and the FLUENT software, in which the heat transfer fluid and physical model are Syltherm 800 liquid oil and LS2 parabolic solar collector from the testing experiment of Dudley et al., respectively. Temperature-dependent properties of the oil and thermal radiation between the inner absorber tube and the outer glass cover tube are also taken into account. Then three typical testing conditions are chosen from the experiment to validate the reliability of the simulation code. Numerical results show that the predicted results agree well with the experimental data, the average relative error is within 2%. And then the mechanism of the coupled heat transfer in the receiver tube is further studied.