Using the analysis technology of single mass spectrometry, tandem mass spectrometry and single hydrocarbon carbon isotope, 24 oil samples in Huizhou Depression were detected and the understanding of the sources of complex crude oil types was made. The study results show that the oils in Huizhou Depression can be divided into three types. The carbon isotope of isoprenoid hydrocarbons of mixed oils show two different characteristics, which are δ¹³CPr>δ¹³CPh and δ¹³CPr<δ¹³CPh. Pr is rich in ¹³C relative to Ph, which shows that methanogenic bacteria can constitute additional inputs of phytane. Oils originated from the middle-deep lacustrine source rocks in Wenchang Formation generally have heavy δ¹³C value. Blooming of algae can result in an enrichment of 13C.