The series compounds La1-xCaxMnO3 (x=0-0-1.0) are synthesized by the wet chemical method. When x<0.5, the crystal structure of La1-xCaxMnO3 belongs to cubic system, when x greater than or equal to 0.5, that of La1-xCaMnO3 belongs to orthorhornbic system. The relative contents of the C Mn4+ ion in the series compounds are determined by the chemical analysis methods. The relative content of the Mn4+ ion in La1-x,CaxMnO3 increases gradually with increasing the calcium ion content. When x greater than or equal to 0.5, there is neither the oxygen excess nor the lanthanum deficiency in the compound. The tolerance factor of La1-xCaxMnO3 is calculated and no anomaly in the variation of tolerance factor of La1-xCaxMnO3 with x is found. The catalysis activity of La1-xCaxMnO3 for NOy reduction by C3H6 varies with x and there is a minimum in the variation of the largest conversion efficiency for NOy reduction with the composition of La1-xCaxMnO3. (C) 2004 Published by Elsevier B.V.