Abstract-The purpose of this research are to develop a Student Activity Sheet on discovery-based learning of Basics Laws of Chemistry and test the validity and practicality of LKS produced. This type of research is the Research and Development (R & D). Development models used in this study is a four D models, namely (1) define , (2) design , (3) develop and (4) disseminate. This study is limited to the development stage. The instrument used in this research is the questionnaire of validity and practicalities. LKS developed validated by 7 people validator, consisting of five chemistry lecturers and two chemistry teachers. Practicality test carried by four chemistry teachers and several X grade students of MAN 3 Padang. Based on the research that has been conducted, the product produced Student Activity Sheet discovery-based learning for material Basics Laws of Chemistry that its validity and practicality had been examined. LKS produced has an average value of 0.90 with the validity of the category of very high validity, average of teachers practicality is 0.85 with very high practicality categories and average of students practicality is 0.72 with high practicality category.