The main objective is to study the inhibitor effect of hydroalcoholic extract of Achyranthes indica Linn. on the crystallization of calcium oxalate in synthetic urine. Our study of the calcium oxalate crystallization is based on change in turbidity followed at 620nm by means of a spectrophotometer. The calcium oxalate formation is induced by the addition of 0.01M sodium oxalate solutions in synthetic urine. The addition of inhibitor with various concentrations (10%, 20%, and 40%) enabled us to give information on the percentage of inhibition. The comparison between the turbidimetric slopes with and without inhibitor gives the effectiveness of inhibitor for the hydroalcoholic extract. By comparing the photomicrographs of with and without inhibitor, we concluded that the extract of Achyranthes indica Linn. acts on nucleation as well as crystal growth stage. The hydroalcoholic extract of the extract of Achyranthes indica Linn. remarkably inhibits of crystal formation in calcium oxalate urinary lithiasis.