Abstract: his paper summarized the contributing factors of low resistivity hydrocarbon bearing zones after studied the log evaluation difficulties which existed in the low resistivity hydrocarbon reservoirs in the Third Section Zone of Dongying Group in Hainan 8 block. The author found that it was very difficult to find the difference between oil bearing zones and water bearing zones during the research. The author also pointed out that the main reasons were finding reservoir lithology, high saturation of irreducible water and high salinity mud filtrate invasion. Meanwhile, the hydrocarbon distribution trend in the block after the correlation between test data and the auxiliary data were known and could offer reasonable basis and measure for the further development of that block.