Morphological differences were studied using the analysis of variance between various partial length and shell length of three populations of Saxidomus purpuratus on the Korean waters. The Relative growth equations, that is, SH-SL, SW-SL, TW-SL of S. purpuratus by sex were estimated. The analysis of variance of four morphological characters proved that each population has no sexual differences (p>0.01). But the three populations are significantly different in morphological characters (p<0.01).