As a result of COVID-19, various forms of education and teaching are moving online. However, the notion of an online STEM camp is still in its beginnings, and there is little relevant research and experience in this context. At the beginning of April 2021, the research team launched an online STEM charity camp with the theme of "Shen Nong Tastes Herbs." Participants included 113 third- and fourth-grade primary school students ranging from 8 to 12 years of age from four schools in Karamay, Xinjiang Uygur Autonomous Region with weak educational capabilities. The camp lasted for 3 days and included 7 activities, while remote teaching was accomplished through "Dingtalk." Pre- and post-test questionnaires and interviews were used to explore the impact of this camp on students. We found that online STEM camps could improve students' self-efficacy, computational thinking, and task value, and there is a significant improvement in the self-efficacy (p = 0.000) and task value (p = 0.001) dimensions. In addition, students with high self-efficacy had higher scores in the other two dimensions. Finally, we summarized the experiences and gains of students and teachers and proposed suggestions for developing online camps based on this experience.