In order to overcome the shortcomings of existing sulfate scale detergent and increase scale removal rate by enhancing the synergistic effect between chelating agent and additives，a kind of chelating agent-based alkaline detergent named as SA-209 was developed. The effects of SA-209 concentration，descaling time，pH value，temperature，and salt concentration on the scale removal rate for barium and strontium sulfate scale were evaluated. The results showed that with the increase of SA-209 concentration， descaling time and temperature，the scale removal rate of SA-209 to barium and strontium sulfate scale increased first and then gradually stabilized；with the increase of pH value，the scale removal rate increased first and then decreased；and with the increase of KCl concentration in the solution，the scale removal rate decreased slowly. The optimum descaling condition of SA-209 to barium and strontium sulfate scale was obtained as follows：4%—12% SA-209 dosage，4—12 h descaling time，11—12 pH value，80—120℃ descaling temperature. The scale removal rate of SA-209 to barium and strontium sulfate was about 55% and 65% respectively，and to scale sample in offshore oilfield with barium sulfate as the main component was 72.4%. The corrosion rate of 4% and 12% SA-209 on N-80 steel sheet was 0.2022 and 0.4412 g/（m2·h）respectively，which was significantly lower than that in industry standard. SA-209 had high scale removal rate and low corrosion to equipment or tubing which was suitable for the scale undissolved by acid.