Abstract: Low-resistivity reservoir is abnormal. Its resistivity of pay zones is usually close to or sometimes lo wer than that of adjacent water-bearing zones. On the basis of research rock's type, granularity, clay mineral's ingredient and distribution, pore texture, water affinity and concentration of formation water of the fifth section in Huagang Formation, it's found that the most important factors causing low resistivity of pay zones are higher irreducible water saturation and high concentration of formation water. The chief reasons of the low resistivity oil formation are high action ex change, high irreducible water saturation and high salinity water etc. The methods of interpretation are best to identify low resistivity oil formations that in common use are introduced. Mo re parameter network interpretation method is the best.