Abstract: Most Chiness crude oils are high in nickel and low in vanadium content.By means of liquid chromatography,chemical treatment,UV-Vis spectrometry,mass spectrometry and atomic adsorption spectrometry,the nickel compounds were separated into three groups,i.e.,weak polar nickel compounds,nickel porphyrins and strong polar nickel compounds The content of nickel porphyrins in Gaosheng,Wangguantun,Yangsanmu,Shengli and Gudao crude oils were determined.By means of mass spectrometric technique,DPEP,ETIO,DI-DPEP,RHODO-ETIO and RHODO-DPEP were identified in Gaosheng crude oil.DHODO-DI-DPEP might also be present in Gaosheng crude oil.The evolution of DPEP to DI-DPEP and RHODO-DPEP has been presumed as an isomerization,dehydrogenation and disproportionation process,and the existence of various types of nickel porphyrins shows that such metal chelate compounds were quite stable under geological conditions.