This study aims to produce student worksheets (LKPD) assisted by PhET Simulations on valid acid-base materials and determine student responses to the developed worksheets. This research is a research and development (Research and Development) with development procedures using the ADDIE model, namely analysis, design, development, and evaluation. However, this research was only carried out in 3 stages. Data collection techniques were obtained through interviews, validation of expert sheets and student questionnaires. This study involved 3 expert validators, namely media expert validation, material expert validation, and linguist validation. The research subjects used a one to one scale test consisting of 3 students and a small group scale test consisting of 12 students. The results obtained showed that the LKPD developed was valid, judging from the results of material expert validation, the percentage of 88.4% was categorized as very valid, the results of media expert validation obtained a percentage of 92.7% categorized as very valid, the linguistic expert validation results obtained a percentage of 86,1% categorized as very valid. The results of the students showed a good response to the students seen from the one-to-one scale test of 90.5% classified as very good and 91,2% small-scale test rated very good. Keywords: Acid Base, LKPD, PhET Simulation.