First results of complex research of the Chernobyl cooling pond bottom sediments are presented. The general problematic is considered. Information about vertical distribution of bottom sediments water-physical properties, and also ionic compound and radioactive pollution by 137Cs and 90Sr of pore water is received. The inventory of bottom sediments pore water activity is calculated. Strong correlations between concentration in pore water of 137Cs, K+, NH4+ within the selected sediments columns are found out. Results of researches are intended for the forecast of radioecological situation change in the cooling pond water-soil complex during drying-up.