Calcium phosphate is one of the most important inorganic constituents of cheese whey, a by-product of cheese with many nutritive constituents such as proteins, lactose, fat and inorganic salts. To recover proteins from cheese whey, membrane separation has been applied industrially. In this process calcium phosphate Causes fouling by precipitating on the membrane Surface. As a means to inhibit the precipitation, We Studied the effect of adding chelating agents, EDTA (ethylene diamine tetraacetic acid) and citric acid. Experiments were conducted using calcium phosphate Suspension as a model solution of whey and a Solution of whey protein isolate (WPI) in distilled water. With the calcium phosphate suspension, calcium ions in solution were trapped by chelation, and the amount of calcium phosphate precipitation decreased. With the WPI solution, the free calcium ion concentration in solution decreased.