Abstract: Songkhla Lake (SKL) in Southern Thailand is regarded to become shallow and excavation of the lake floor is required in the near future. So the middle part of the SKL has been selected for determining depositional rate and heavy metal concentrations and distribution of the SKL sediments if or not they are being dug will effect to the environments. In this study, composite stratigraphy of the lake sediments from 50 drill cores are constructed, sedimentation rate is then determined using stratigraphy and geochronology and heavy metal concentrations of lake sediments are evaluated. Comparison has been made for heavy metal concentrations of the SKL studied sediments with those of the standards. The result on stratigraphic correlation shows the SKL study area consists of 6 sediment layers with the overall thickness of about 6.5 m. The two oldest layers (up to 2 m thick) took place in Pleistocene whereas the overlying layers (up to 4.5 m thick) are of Holocene age. The study SKL sediments have been deposited at the average rate of ca. 0.37 mm year-1 and becomes the highest (up to 5 mm year-1) in the youngest layer. This implies that sedimentation become accelerated by anthropogenic activity. The results of heavy metal analyses on sediments reveal that heavy metal contents quantitatively lower than those of the Hong Kong, Dutch and US standards. A few (<0.05%) heavy metals (viz., As and Cu) show the values higher than those of the standards. Therefore, the SKL sediments can be excavated without any environmental problem.