This study examined the interaction effects of self-explanation and game-reward strategies on sixth graders' algebra variable learning achievement, learning attitude, and meta-cognitive awareness. A learning system was developed to support the learning activity, and a 2×2 quasi-experiment was conducted. Ninety-seven students were invited to participate in this experimental instruction and assigned to four groups: self-explanation with game-reward, self-explanation, game-reward, and control. The results showed that (1) a significant interaction effect was found on the students' learning achievement of algebra variable: the self-explanation with game-reward group performed significantly better than the self-explanation group, and both the game-reward group and self-explanation group scored significantly higher than the control group; (2) a significant interaction effect was found on the students' learning attitude toward algebra variable: the self-explanation with game-reward group reported significantly more positively than the self-explanation group, and the control group responded significantly more positive results than the self-explanation group; (3) no significant interaction effect was found on the students' meta-cognitive awareness of algebra variable learning: while the game-reward did not show a significantly positive effect, the self-explanation did.