为判断原油顶空气轻烃参数的准确性，采集柴达木盆地西部地区6口井的原油和伴生气，对比分析了原油顶空气和天然气中轻烃的组分和单体烃碳同位素特征。结果表明：顶空气中的C₅—C₇轻烃化合物含量比天然气中的轻烃化合物含量高，但两种方式得到的轻烃相对含量接近；在利用轻烃参数研究油气成因类型、生成温度等方面，两种方式得到的结果相近，但在利用庚烷值和异庚烷值判断油气成熟度时，会得到不同的结果；顶空气较天然气具有整体偏重的轻烃单体烃碳同位素特征，其中环烷烃碳同位素偏重幅度最小，并且两种方式得到的甲基环己烷碳同位素值（δ¹³ C_MCC6）相近。可见，利用原油顶空气可准确获取主要的轻烃参数和δ¹³ C_MCC6，研究成果为丰富轻烃地球化学在油气成藏中的应用提供了依据。

To determine the accuracy of the light hydrocarbon parameter obtained from the headspace gas, crude oils and associated gases from six wells in the western part of the Qaidam Basin were collected. The composition and carbon isotopes of individual light hydrocarbons from headspace gas and natural gas were analyzed and compared. The results show that the content of C₅—C₇ light hydrocarbons obtained from headspace gas is higher than that in natural gas, but the relative contents of each light hydrocarbon obtained from two methods are similar. It is found that light hydrocarbon parameters calculated from headspace gas and natural gas share similar results in studying the genesis type, generation temperature and other aspects, but get different results in evaluating the maturity by using heptane and isoheptane values. Besides, the carbon isotopes of individual light hydrocarbons in headspace gas are greater than those in natural gas, among which cyclo-alkanes have the smallest carbon isotope difference. Particularly, the carbon isotopes of methylcyclohexane (δ¹³C_MCC6) in the headspace gas are close to those in natural gas. Therefore, the main parameters of light hydrocarbons and δ¹³ C_MCC6 can be accurately obtained from the headspace gas of crude oil. The research results provide a basis for enriching the application of light hydrocarbon geochemistry in oil and gas accumulation.