The purpose of this study was to explore the effects of Bloom’s mastery learning upon the achievement and learning attitude in science and technology of elementary school children. The major findings of this study are as follows: 1. In the science achievement (1) there are significant differences in the science achievement of post-test scores of the three groups. The science achievement of the E1 group is the best; (2) the comparison between pretest arid post-test, the variation of science achievement of the El and E2 groups tended to decrease significantly. 2. About attitude towards science learning (1) the total scores of children’s attitude towards science learning of the El and E2 groups are higher than the control group significantly; (2) the separate score of children’s attitude towards science learning, in the ‘learning interest’ item, the scores of the El and P2 groups are higher than the control group significantly; in the ‘learning anxiety’ item, the score of the El group is higher than the control group significantly ; in the ‘usefulness of science’ item, the scores of the El and E2 groups are higher than the control group significantly.