Equation of state of detonation products possesses various types of mathematical expressions which describe the relation between pressure and volume. Jones-Wilkin-Lee (JWL) equation of state is a widely used equation of state of detonation products because of its simplicity in hydrodynamic calculations. The JWL equation of state may accurately describe the process of expansion drive of detonation products. The JWL equation of state contains parameters, and describe the relation among the volume, energy and pressure of detonation products. These parameters may be determined by detonation experimental data and numerical method. Traditional numerical method is adjusting parameters based on experimental data and numerical experience. Obviously, artificial ingredient may affect the calibrating result in traditional method. This paper uses the Bayesian method to determine the unknown (uncertain) parameter of JWL equation of state for detonation products. The method can calibrate the uncertain parameters based on the known parameter information, the experimental and simulating data. The results of the paper are consistent with those in the reference papers. By theoretical analysis the calibration result accords with the physical signification of the parameters of JWL equation of state. The epistemic uncertainty is slightly reduced. The calibration result collects all the parameter information in the prior parameter information, experimental data and numerical results. The experimental data are totally included in a 90% confidence interval of simulation. The numerical result shows that this method can be used to study the uncertain parameter of JWL equation of state for some sample explosives. Especially, the method reduces the artificial ingredient in the parameter calibration.