Abstract: In order to investigate influencing factors that making different of calcium ion chelating power in different products,self-indication volumetric precipitation method was employed to survey sodium tripolyphosphate′s calcium chelating capacity.Influences of polymerization temperature,polymerization time,cooling rate,and neutralization degree on calcium chelating capacity of sodium tripolyphosphate were also studied. Results indicated that different products have obvious difference in aspect of calcium ion chelating power,though their mass fractions of sodium tripolyphosphate all reached about 95%;polymerization time has the biggest inlfuence on sodium tripolyphosphate calcium chelating power,cooling rate was second influencing factor,and inlfuences of neutralization degree and polymerization temperature were less.