The trend to extend science education to include STEM education in the US in the recent decade also takes place in many other countries in the world. In Hong Kong, the future development in education proposed in the Policy Address 2015 included: “The Education Bureau will renew and enrich the curricula and learning activities of Science, Technology and Mathematics, and enhance the training of teachers, thereby allowing primary and secondary pupils to fully unleash their potential in innovation (item 152).” However, the integration of science with technology, mathematics and engineering is still to be established and further research along this line is necessary. Therefore, this study attempts to analyze the written reports in an inquiry project event for a better understanding of STEM activities demonstrated by the primary students. The primary students’ inquiry project reports were chosen from those 140 teams (with 4-5 members in a team) with 1000 primary students who were aged 10-12 participated in the 2015 “Innovations in Science and Environment Studies” event in Hong Kong. Under the main theme of “Go Green at Home”, the participating teams had to present the processes and results of their inquiry projects and to submit a written report which recorded their ideas, methodology and inquiry processes and results. 10 project reports were randomly chosen from each group of outstanding, merit and consolation projects with a total of 30 projects being analyzed. Content analysis was first conducted to code STEM activities demonstrated in each project report. The coded data were then changed into numerical data for quantitative analysis. The results showed that more engineering and science activities were adopted than technology and mathematics activities in the inquiry projects. Outstanding group conducted more STEM activities than the merit and consolation groups and significant group differences existed in science and mathematics activities. Furthermore, science activities