Writing is the difficult skill for the students. Nevertheless, it is should be mastered by Junior High school students. According to the interview, pre-test and post test given to the students in preliminary study, it was found that the major problems they faced were how to develop ideas. The teacher also never gave model of how to write descriptive, because writing activities in class were boring and their teacher is monotonous in teaching. Besides that, her strategy was not interesting, To solve the problem, one of the strategy used in teaching writing is think pair share. Think pair share is one of cooperative learning methods. This strategy is used to improve student's writing ability in this study. The research problem is How can the implementation students’ writing ability in descriptive text by using think pair share strategy of the seventh grade at SMPN 1 Semen Kediri and How is the result of students writing ability in descriptive text by using think pair share strategy of the seventh grade at SMPN 1 Semen Kediri. This study used collaborative classroom action research following Kemmis & Taggart. The researcher designed the lesson plans and set the criteria of success. The research was conducted in two cycles. Each cycle consisted of two meetings which covered: planning an action, implementing the action, observing the action, and reflecting on the observation. The subjects were 38 students of VII-C in SMPN 1 Semen Kediri in academic year 2015/2016. The instruments used to collect data observation checklist and test of the students. The criteria of success used in the study are the students’ mean score of writing at least 75 and 80% of the students score in writing at least 75. The research findings indicated that the students’ are active and motivated during the teaching learning process. The students writing ability have good improvement after being taught by using think pair share strategy. The steps of think pair share strategy in writing descriptive text, such as: (1) explain about TPS strategy and descriptive text. (2) asking students to tell about the descriptive text (3) giving a topic or question about illustration. (4) asking students to think of solution from the problem. (5) students discuss their solution with their partners. (6) calling on few students randomly to present their ideas with the rest of the class. (7) asking students to respond or feedback. (8) asking them to write what have been discussed in descriptive text. The result showed that think pair share strategy successfully helped in improving the students’ writing ability in writing descriptive text. In cycle 1 was 47.8% of subject who classified into a success with the average was 73.52 and in cycle 2 was 92.2% of subject who classified into a success with the average 79.71. Based on the result of this study, it can be concluded that the effort to think pair share at the second semester of the seventh grade students of SMPN 1 Semen Kediri can improved the students’ writing ability. It is recommended of research were: (1) for the teacher should apply think pair share as in teaching learning process especially in writing descriptive text. (2) for the students the think pair share strategy can help the students to good writer and can improve writing ability. (3) for the next researcher was hope to look at the condition of the students and school because every condition of the students and school have different characteristic therefore the researcher does the pre-test doing the research.

Key words: Improving writing ability, Descriptive writing, Think pair share