The relationships between the stability of W/O emulsion in five typical blocks of Shengli oilfield and the compositions of heavy oil, including the content of polar fractions, heteroatom and transition metals, as well as the properties of heavy oil, such as the mean dipole moment of polar fractions, were studied by gray correlation entropy method. At the same time, the microcosmic image of W/O emulsion and the Zeta of polar fractions were also studied in order to analyze the stability mechanism of W/O emulsion. SV value was used to represent the stability of the emulsion, the larger of SV value, the more stable of the emulsion. The results showed that four polar fractions, three heteroatoms and three transition metals were arranged according to the degree of association with SV value in following order: resin (0.9945)>saturate (0.9928)>aromatic (0.9901)>asphaltene (0.9597), N(0.9993)>O (0.9918)>S (0.9667), Ni (0.9891)>Fe (0.9852)>V (0.9845). The degree of association between the content of resin, N and Ni and SV value were the biggest which indicated that they were the main factors influencing the stability of W/O emulsion. The polar fractions were arranged according to the degree of association between mean dipole moment and SV value in following order: resin (0.9929)>asphaltene (0.9916)>aromatic (0.9796). The mean dipole moment of resin was the key factor that affecting the stability of emulsion. The mean dipole moment of resin was the key factor influencing the stability of W/O emulsion. The W/O emulsion of heavy oil in 3-12-182 block was the most stable with the biggest Zeta of polar fraction absolute value, the smallest of droplet size, the most concentrated size distribution (0.5—1.5) of droplets and the largest SV value (1026.70)