To clarify relationships between the oxic-anoxic environments on the bottoms of the brackish coastal lake and the effect of the tidal current，the distributions of total organic carbon(TOC), total nitrogen(TN) and total sulfur(TS) contents have been investigated in the surface sediments of Lakes Nakaumi and Hamana. Cored sediments in Lake Nakaumi were obtained at 83 stations. And surface sediment samples in Lake Hamana were obtained at 40 stations. Top 1cm of the sediments from the two lakes were analyzed using a CHNS elemental analyzer. TOC contents of Lakes Nakaumi and Hamana ranged within 0.14-4.40% and 0.01-4.94%, respectively. TN contents ranged within 0.05-0.65% in Lake Nakaumi and 0.02-0.53% in Lake Hamana, and TS contents ranged within 0.09-5.42% and 0.05-3.11%, respectively. C/N ratios showed about 7-8 at most area of the two lakes. C/S ratios showed 1.0-1.5 in Lake Nakaumi and 1.5-2.0 in Lake Hamana, respectively. TOC, TN and TS contents showed lower values and C/S ratios showed higher values near mouths of the both lakes. With increace in the distance from the mouth, TOC, TN and TS contents increased and C/S ratios decreased. In addition, C/S ratios in Lake Nakaumi are generally lower than that in Lake Hamana. These suggest that the areas near the mouth of lake have more oxic bottom environments, and the bottom of Lake Nakaumi is more anoxic than that of Lake Hamana. This is probably related with the tidal effect.