The mantle fluids play an important role during the plutonic processes of mantle metasomatism, partial melting, and mantle chemical heterogeneity etc. The immediate information of mantle fluids such as their composition and nature have been effectively obtained by the study of the fluid components hosted in mantle xenoliths, but there are distinct differences in the results of different experimental methods. The present paper makes a comparison between the different experimental methods which are widely used in the determination of fluid composition in mantle-derived rocks and discusses the advantages and applications of each method. Based on the particular milieu (high temperature and pressure) in the mantle where mantle fluids exist, it is suggested that the determined results of fluid composition in mantle-derived rocks with the stepwise heating mass spectrometry method can comprehensively represent the real composition of the mantle fluids. It is essential for the reliability of data that effective sample treatment, reasonable pyrolysis apparatus and system backgroud be employed in the experimental and calculation processes, and different types of fluid components can be separately studied by controlling the heating temperature.