Early generation stability of 8415, a japonica rice variety, was retested by using allelic differences of two qualitative traits. Results showed that both glume tip color and waxy endosperm segregated in progenies of single F1 plants derived from two crosses of 8415/Zi 18 (purple color) and 8415/Dahuaxiangnuo(waxy). The results denied the conclusion obtained in previous studies that 8415 had a characteristic of early generation stability. Meanwhile, it was found that using coefficient of variation as an indicator of early generation stability was unreasonable by analyzing plant height as an example. Importance of avoiding systematic error in research works was also discussed.