The aim of the study was to know the effect of using a strategic of quintet learning cycle in teaching a Mathematics Unit for seventh grade in improving mathematical achievement and thinking for students in the Abyan governorate- Republic of Yemen. The researchers follow experimental approach with the pre post tests. The study sample composed of (80) students, who were divided into two groups, experimental, and control groups. The researchers being sure that the two groups were equivalent in extraneous variables. The experimental group were (40) students who were taught using quintet learning cycle strategy. The control group were(40) students taught in the usual way. The researchers prepared two tests, the first was an achievement test (24 statements), and the second was mathematic thinking test (24 statements). Validity and reliability for the two tests were conducted. The appropriate tools for data statistical analysis were used.

The results of the research showed that there were significant differences in means of math achievement, skills of mathematic thinking (generalization, induction, expression symbols, logical thinking and mathematical proof) for the two groups, in favour of students of the experimental group, who studied by using a strategic of quintet cycle. Also,  there was significant difference in testing mathematical thinking as a whole, in favour of students of the experimental group,  However,  there was no statistically significant difference between the experimental and control groups at the skill of the elicitation.

Key words: a strategic of quintet cycle of learning. Achievement. Mathematical thinking.