The discovery of LF14 oil-bearing structure in Pearl River Mouth Basin suggests that Wenchang Formation in Lufeng Sag has significant potential for oil and gas exploration. However， exploration practice reveals that the physical properties of sand bodies in the same sedimentary facies belt vary greatly. The influence of diagenesis on the physical properties of reservoirs is not clear， which restricts the prediction of high-quality reservoirs in the study area. In order to predict the favorable zones in lowpermeability reservoirs， the diagenetic facies of sandstone reservoirs of Wenchang Formation in Lufeng Sag was studied based on thin section identification， scanning electron microscopy， X-ray diffraction， and physical property testing， along with drilling data.The favorable zones in low-permeability reservoirs in the study area were predicted by diagenetic facies delineation. The results show that reservoirs of Wenchang Formation primarily consist of quartz sandstone， which has a high degree of maturity in composition and structure. The reservoir space is characterized by interparticle dissolution pores. Four distinct diagenetic facies are identified in the study area， including moderate compaction-weak cementation-strong dissolution， strong compaction-moderate cementationmoderate dissolution， moderate compaction-strong cementation-weak dissolution， and strong compaction-moderate cementationweak dissolution. Among these facies， the moderate compaction-weak cementation-strong dissolution is the most favorable facies in the study area， with the majority of the facies occurring in the underwater distributary channels. The strong compaction-moderate cementation-moderate dissolution has the second most favorable physical properties and is mainly developed in the mouth bars. The moderate compaction-strong cementation-weak dissolution and the strong compaction-moderate cementation-weak dissolution are unfavorable diagenetic facies. Vertically， the diagenetic facies types of the reservoirs are comprehensively identified based on well logging data by utilizing petrophysical parameters and physical properties. Laterally， through the analysis of the correlation among diagenetic facies， seismic acoustic impedance， and Poisson’s ratio， it was found that the moderate compaction-weak cementationstrong dissolution and the strong compaction-moderate cementation-moderate dissolution have relatively low Poisson’s ratios，while unfavorable diagenetic facies have relatively high Poisson’s ratios. On this basis， Poisson’s ratio inversion results are used to predict the favorable zones in low-permeability reservoirs in the study area.