This research was aimed to develop proper learning material using guided inquiry and reflective thinking can be used to practice critical and creative thinking skills. This research was conducted 4-D models, i.e. define, design, develop, disseminate. This type of research is descriptive quantitative research design with one group pretest posttest design. The samples used in the study were eleventh grade students of SMAN 20 Surabaya. The parameter of this research measured validity, practical, and effectiveness of the learning package. Research result: validity syllabi, lesson plan, reflective thinking paper, students worksheet, attitude paper, psychomotor paper, knowledge paper, so generally the result validity of learning material is proper. The practical of using learning material can be seen from what lesson plan had been done on proper category. The effectiveness of learning material can be seen from scores pre-test and post-test which has n-gain. N-gain in the pretest and posttest is declared increased: 0,87 for critical thinking skill and 0,83 for creative thinking skill are means high rate. Based on this research, guided inquiry and reflective thinking can be used to practice critical and creative thinking skills. The validity, practically and effectiveness of learning material shows that the learning package using guided inquiry and reflective thinking is proper and can be used to increase the critical and creative thinking skills of students.

Keywords : Guided Inquiry, Reflective Thinking, Critical and Creative Thinking Skills.