This study is a classroom action research. The general objective of this study is the effectiveness of outdoor activities for improving students’ writing descriptive text. While the specific objective of this research is: What is the improvement made by students in writing descriptive texts by the outdoor activities? The procedure of the research consisted of planning, action, observation and reflection. The data was collected through tests which were delivered into the pre-test and post-test. The research result: (1) Using outdoor activities as a method can improve students writing skill, It is proved with the students’ improvement score of the tests because mean of post-test in cycle 1 is higher than mean of pre- test (66.17>55.24), the mean of post-test 2 in cycle 2 is higher than mean of post-Test in cycle 1 (70.10>66.17) and the mean of the mean of post-Test of the cycle 3 is higher than post-Test in the cycle 2 (77.31> 70.10). The proven target is 78% or 22 students who increase their writing skill. (2) The significant improvement of using outdoor activities in improving students writing skill is proved from the result of t-test and t-table in cycle 1 (9.30>2.042) which the score of t-test was higher than the score of the pre-test and t-table in cycle 3 (13.69>2.042) also showed that the score of t-test was higher than the score of t- table of the cycle 1 and cycle 2. Here the result of the t-test and the t-table in cycle 2 low (5.13 >2.042).