The purpose of this study is to determine a valid, practical, and effective Guided Inquiry learning material to improve students' science skills process. Guided Inquiry with REACT strategy to improve students' science skills process in the calor material of Class V on sixth Theme of second Sub Theme. This research is a research development of learning materials that refers to the Rick and Carey development model and tested on fifth grade students in Romokalisari 132 Surabaya with One Group Pretest-Postest Design. The tools to be developed are the syllabus, lesson plan, Student Textbooks, and Student Worksheets, and science skills process tests. Practical learning materials based on the implementation of lesson plans that are categorized as good and active student activities while learning and they are effective based on the results of the Science Skills Process test that shows of 11 students have high n-gain and 4 students categorized as moderate n- gain and got very good student response. It can be concluded that the Guided Inquiry based on learning material with REACT strategy is valid, practical and effective so that it is used to improve the science process skills of fifth grade students on sixth theme of second Sub Theme in calormaterial.

Keywords : Learning Material, Guided Inquiry, REACT Strategy, Science Skillsprocess.