The purpose of this study was firstly to investigate the mathematical metacognitive characteristics of high-efficiency students by comparing high-efficiency and low-efficiency students. Secondly, the aim was to explore the pathways of mathematical metacognition of efficient mathematics learners in mathematics achievement. In this study, second-year Chinese middle school students were divided into a high-efficiency group (n = 297) and a low-efficiency group (n = 203) according to their learning efficiency in mathematics. The results indicated that the mathematical metacognitive knowledge and mathematical metacognitive monitoring of the students with high efficiency in mathematics learning were better than those of the other group. Their mathematical metacognitive characteristics were mainly reflected in the five dimensions of regulation, inspection, knowledge about individuals, knowledge about tasks, and knowledge about strategies. Furthermore, path analysis revealed that both mathematical metacognitive monitoring and mathematical metacognitive experience directly affected the mathematics achievement of students in the highly effective group. Mathematical metacognitive knowledge had an indirect effect on mathematics achievement. The findings imply that teachers should focus on the guidance of mathematical metacognition in mathematics instruction.