In the digital era, in order to develop the core literacy of Chinese students, the chemistry class in the third day of junior high should effectively use Internet, artificial intelligence and other technologies to improve teaching and learning. ST analysis method is to record and analyze the system of multiple interactive elements of teachers and students with the help of digital technology, and obtain the analysis of classroom type and teaching effectiveness, so as to enable teachers to study effective classroom teaching. The lesson of "common salt in life" is the key and difficult point of ninth grade chemistry. With the help of ST analysis method, classroom observation and analysis were carried out, and effective teaching strategies were obtained.