This research aimed to explore the effects of the implementation of different curriculum designs in strengthening the mental toughness among low-grade students in elementary school. Methods: The participants and subjects of this research were one physical education teacher and his two classes that included 64 students, 32 students each class. We manipulated following four factors: activeness and striving, the setting of goal, self-confidence and the pressure of competition. Through practical teaching, we implemented 30 classes of mental toughness for sport in experimental group and of jogs the technology and the physical ability training in control group. With specialty mental toughness for sport and state mental toughness for sport, we implemented six classes of pre-test and post-test. The data collected was analyzed by two-way ANOVA and one-way MANCOVA. Results: The findings were: on the trait and state mental toughness for sport: after teaching, the students of both experimental group and control group had significant progress whereas the experimental group were significantly higher than that of control group. On four manipulated factors: after teaching, activeness and striving, the setting of goal, self-confidence and the pressure of competition of students of experimental group showed significant progress. The effects of curriculum designs were arranged in order from high to low as follows: the setting of goal, activeness and striving, self-confidence and the pressure of competition. Conclusion: Therefore we might know that students' mental toughness had significant progress by teaching the curriculum of mental toughness. They could achieve the enhancement of decision-making ability, positive attitude of problem-solving, concentration, self-confidence, and also could promote the teaching goal of pressure control and pressure-relieving.