The aims of this study were to analyze the senior high school student's written communication skills on the subject of chemical basic laws taught by using ELPSA (Experiences, Language, Picture, Symbols, and Application) learning design. The type of this research is descriptive quantitative. Subject of this research was 33 of 10 th grade science students at SMA Negeri 8 Samarinda, East Kalimantan, Indonesia that were chosen by using purposive sampling technique. The written communication skills were analyzed by using post-test. It consisted of (1) Ability to express ideas; (2) Ability to explain observation results; (3) Ability to communicate data processing and analysis; (4) Ability to conclude research results and to communicate the conclusions based on the data; (5) Ability to present the data in the form of tables, graphs, flowcharts and concept maps; (6) Ability to present figure of experiment equipment; (7) Ability to specify the research variables; and (8) Ability to present the model of relations with international symbols and standards. The results showed that the written communication skill of the subject research was 44.60, categorized as sufficient capability. Therefore, there should be further development and research to increase student ability on written communication.