. The purpose of this research is to analyze the effectiveness of Project Based Learning (PjBL) of writing skills on Science teaching materials to elementary school teachers candidates.This research used experimental methods (single-one group pretest-posttest design) with instruments such as portofolio assessment sheets, observation sheets, and questionnaire sheets .The effectiveness of analyzing used n-gain and t-test .The subject of this research is elementary school teachers candidates who contracted “Science Learning”subject in a program study teacher education of elementary school at University Muhammadiyah Cirebon. The findings of this study has produced a contextual book for Science teaching material. In addition, there is an increased of elementary school teachers candidates who prepared the teaching materials in a printed form relevant to the needs and characters of the students as well as the curriculum. It is proven by assessments that the ability rose significantly from 2,71 (category is adequate skill) to 3,83 (category is skilled) and supported by the n-gain value at 0,87. Based on the t-test count of 8,050 larger than t-table 2,045. Recommendations from this research is that PjBL as a learning model could become one of the alternative learning models to improve writing skills material for elementary school teachers candidates.