The students' low science process skills are caused by learning that is still dominated by the teacher, so it is necessary to develop a learning approach that focuses students in the learning process. One approach that can be used is learning that integrates science, technology, engineering, and mathematics (STEM). This study aims to measure the improvement of students' science process skills that are integrated with the STEM approach on the reaction rate material. This research is a quantitative research with a pre-experimental design type, one group pretest-posttest with a sample of 30 students from class XI SMA Negeri 9 Pontianak, taken by random sampling technique. The data collection tool used is a subjective test of science process skills. The results showed that there was an effect of the STEM approach on the students' science process skills on the reaction rate material, with a score of 76.11, good criteria. Among the aspects of science process skills measured, including observation, classifying, calculating, predicting, inferring, and communication, the communication aspect of students experienced a significant increase from a score of 3.33 to 91.1. This study shows that the STEM approach to reaction rate learning effectively improves students' science process skills.