Research development of student worksheet (LKS) inquiry oriented to improve students critical thinking skills of junior class IX on the theme of Virgin Coconut Oil (VCO ) is intended to describe the feasibility of LKS , improved thinking skills Krtis after learning as well as students' response to a given worksheet . This type of research refers to research and development (Research and Development ) . Development of integrated learning science worksheets using 4D models (Four -D) which consists of 4 stages include the Define phase, Design, Develop , and Destiminate. But in this worksheet development only reached the stage of development at saja.Hasil of development worksheets that have been said to be feasible then tested on students SMPN1 Sedati many as 23 students . This study used a design one group pretest and posttest design . The data in this study was obtained through the study of techniques to get suggestions developed LKS , LKS validation for knowing eligibility and student questionnaire responses to determine students' responses after using worksheets . The results obtained for the feasibility study worksheets that averaged 81.9 % in terms of the feasibility of the content , amounting to 78.3 % of the presentation of the feasibility and viability of 81.7 % of the language . Critical thinking skills of students after administration of BLM -oriented inquiry can improve critical thinking skills of the average 10 % to 74.6 % and the positive response of students to the worksheets that were developed were positive with an average of 91.9 % thus worthy of inquiry -oriented worksheets used in learning process. Keywords: Student Worksheet , Inquiry , Integrated Science , Critical Thinking Skills , Themes Virgin Coconut Oil ( VCO ) , Class IX junior high school students.