Abstract: Reducing exploration risks to the lowest limit and raising the successful probability of exploration are always the aims which geological explorers long for day and night. As the direct targets of hydrocarbon exploration, the correctness of evaluation results for traps will be derectly related to the success or failure of hydrocarbon exploration. Reliable evaluation can effectively reduce exploration risks and raise exploration benefits. By summing up the evaluation methods of conventional traps and according to the theory of hydrocarbon accumulation systems, the theory of reliability is introduced into trap evaluation in this paper, and "the reliability of trap accumulation" and its evaluation train of thought are advanced for the first time. Based on the analysis of subjective and objective factors which affect the reliability of trap accumulation, the geological conceptive model, the mathematical model and the evaluation system for the evaluation of trap accumulation reliability are established. This makes an attempt to further approach the application of the reliability theory to hydrocarbon exploration.