Based on 8 morphological characters between Japanese Meretrix lusoria and two Chinese species of Meretrix,by means of multivariate morphometrics and traditional taxonomy methods,and then we analyzed with One-Way ANOVA,principal component analysis,cluster analysis,discriminant analysis and Mantel test for investigating morphological variations among them and evaluated Japanese M.lusoria species validities.Results and inference are as follows:(1) One-Way ANOVA showed that there were 5-8 significant differences among 8 morphological characters between Japanese M.lusoria and two Chinese species of Meretrix(P<0.05).(2) Results of cluster analysis showed that six M.meretrix populations formed a separate cluster,among which,the southern populations were a cluster while the northern populations were another.Japanese M.lusoria was close to Changle M.lusoria.(3) In principle component analysis,three principle components were constructed by factor loading.The contribution ratios of four principle components were 34.88%,18.61%,16.89%,respectively,and the cumulative contribution ratio was 70.38%.The three dimensional Scatter diagram further indicated that Japanese M.lusoria and Changle M.lusoria had no overlap with the different M.meretrix populations.(4) Eight discriminant functions of Japanese M.Lusoria and two Chinese species of Meretrix were established,and the discriminant accuracy was 39.09%-100% for P₁ and 47.06%-100% for P₂.The average diseriminant accuracy was 70.60%.The discriminant accuracy of Japanese M.lusoria was 100% and that of M.lusoria was above 91.67%.(5) Results of Mantel test showed that geographical distance and Euclidian distance of all Meretrix populations were significant(r=0.623 7,P<0.01).Above results indicate that Japanese M.lusoria and Changle M.lusoria should belong to M.lusoria,which were the different geographical populations.According to the MAYR 75% rule,the results indicated five out of eight morphological characters were above 1.28,so the difference of the two M.lusoria populations was greater than difference between subspecies.