Acidic species were extracted from heavy crude oil by alcohol-alkali solution and ion exchange resin. The acidic species in the obtained extracts and extracted crude oil were characterized by negative-ion ESI FT-ICR MS. The analytical results indicated that some class species, O2, O1, N1, N1O1, N1O2, N1S1 and O2S1 etc., were identified in the negative-ion spectrum, in which O2, O1 and N1 class showed much higher abundance than others. Compared to O1 and N1 class, O2 class could be extracted from heavy crude oil by using the two methods more efficiently, which means that a great majority of O2 class can be extracted; meanwhile, almost half of O1 and N1 class still remained in residual phase. Detailed analysis demonstrated that alcohol-alkali method was effective for extracting O2, O1 and N1 class with lower molecular weight; ion exchange method, however, was helpful to extract higher molecular weight O1 and N1 class and showed almost equal extraction selectivity to all kind of O2 class.