This research was conducted in order to find out whether the use of Peer Editing was effective or not to improve the students' ability of the seventh gradein writing descriptive paragraph at MTS AlkhairaatPelawa. The researcher employed pre-experimental research design. The population was the seventh grade students and VII A1 was the sample. The data of the research were collected through tests which consist of pre-test and post-test. The result of the test shows that there is an improvement on the students' mean score after the treatment. The students' pre-test mean score (40.7) increased to (63.64) thepost-test. It is attested on the ttablewhere the tcountedvalue (9.41) is higher than ttable (1.761). In short, the use of Peer Editing is effective to improve the students' ability in writing descriptive paragraph.