Abstract: Twenty-nine species (or forms) of fossil pollen and spores referred to 23 genera extracted from the petroleum samples taken from the Liaohe oil-field are investigated in this paper. Using the above plant microfossils as indicators, the oil source rock of this oil-field are traced. The spores and pollen extracted from the petroleum reserved in the Shahejie Fomation of the Liaohe oil-field are as follows: Pterisisporites undulatus, Osmundacidites wcllmanii, Plicifera decora, Pinuspollenites labdacus f. minor, Abietineaepolle- nites cembraeformis, A. microsibiricus, Cedripites diversus, Keteleeria dubia, Ephcd- ripites cheganicus, Graminidites sp., Liliacidites sp., Quercoiditcs asper, Retitricolporites sp., Chenopodipollis microporatus, Compositoipollenites sp, etc. The following spores and pollen are extracted from the crude oil reserved in the Dongying Formation of the present oil-field: Osmundacidites wellmanii, Plicifera decora, Pinuspollenites labdacus f. minor, Sparganiaccaepollenites sp., Graminidites sp., Liliacidites sp., Chenopodipollis multiporatus, Compositoipollenites sp., Artemisiaepol- lenites sp., etc. Some Fossil Fungi and Algae are observed from the above mentioned petroleum samples. Comparing the spores and pollen extracted from the petroleum of the Shahejie Formation with those of the sporo-pollen complex of the Shahejie Formation, it may be decided that they all came from the deposits of the Shahejie Formation. This character indicates that the oil source rock should coincide with the oil reservoir rock, and both of them belong to the Shahejie Formation which is referred to Early Tertiary Period. By comparison with the sporo-pollen complexes of the Dongying Formation and the Shahejie Formation, most of the pollen and spores found from the petroleum of the Dongying Formation may be found to come from the Dongying Formation, and the rest of them from the underlying Shahejie Formation. Thus it implies that the petroleum reserved in the Dongying Formation should also originate from the Shahejie Formation.