Abstract: PVT simulation of hydrocarbon inclusions can be used to reconstruct trapping temperature and pressure. Vapour/liquid ratio is an important parameter affecting PVT simulation. However, due to the lack of a hydrocarbon inclusion standard, the accuracy of the vapour/liquid ratio measured by Confocal Laser Scanning Microscope (CLSM) has not been investigated. In this paper it is proposed that a synthetic hydrocarbon inclusion standard can be used for correcting CLSM and the theoretical vapour/liquid ratio of hydrocarbon inclusions can be calculated based on the known hydrocarbon composition, trapping temperature and pressure. The actual vapour/liquid ratio can be obtained by CLSM. The differences between the actual values and theoretical values can be used to calculate the error of actual vapour/liquid ratio, so as to complete the error calibration of CLSM. Experimental results confirm that the absolute error of CLSM with high resolution is less than 0.5%, and thus CLSM can provide accurate parameters for the PVT simulation of inclusions. This study affirms the accuracy of CLSM for determining the vapour/liquid ratio of hydrocarbon inclusions, and further confirms that PVT simulation of hydrocarbon inclusions can provide reliable data for hydrocarbon accumulation.