Writing is a complex process that allows students to explore thoughts and ideas and make them visible and concrete. Teaching writing is a process of giving skills to students on how to communicate and express their thought, feelings, and opinions in a written language. Writing skill is a skill rarely taught to learners either at SMP or SMA level since it is considered difficult, not tested in semester or final examination, teacher is more often preoccupied with explaining the parts (generic structure) of a text than by applying it in a student's writing, and learning writing skills is very time consuming in the process and also in providing feedback. This article is derived from the study conducted on finding the effect of collaborative writing strategy and writing interest toward students' writing ability of descriptive text at tenth grade of SMA INS Kayutanam. The aim of the research was finding out whether or not collaborative writing strategy could give a better result of students' achievement in writing descriptive text. This was a quasi experimental study taking 44 students as the participant. The data were collected by giving writing test. The students were asked to a write a descriptive text based on the picture given. The result of the test shows that the students had better achievement in writing descriptive text when they were taught by using collaborative writing strategy.