The sediment cores were collected from four sites of Lake Shinji, Japan. The unsupported ²¹⁰Pb (²¹⁰Pb_excess) in surface layer ranged from 12 to 19 dpm/g, while the radium-supported ²¹⁰Pb was 1.4∼1.9 dpm/g. The ²¹⁰Pb_excess profiles decrease logarithmically with depth. Thus, the ²¹⁰Pb dating method is applicable for these cores. Taking into account the compression effect of sediments, the accumulation rates of Lake Shinji sediments for surface layer have been estimated to be 0.3∼0.5 cm/yr. The sedimentation rates range from 0.071 to 0.13 g/cm²·y.