Learning motivation is crucial to online learning success, especially for K-12 students. Although previous research has proved that there are many factors influencing online learning motivation, few studies have systematically investigated this phenomenon from the integrated perspectives of community of inquiry and technology acceptance, two theoretical frameworks that are commonly used to explain experiences of and attitude towards online learning. This study investigates the effects of K-12 students' perceived presence and technology acceptance on their online learning motivation. A total of 13,610 valid questionnaires were collected from K-12 students from Wuhan and adjacent areas in central China participated in the survey. The findings reveal that: (1) perceived usefulness, self-efficacy, social presence, and perceived ease of use have a larger positive effect on online learning motivation, while cognitive presence has a small positive effect on online learning motivation; (2) teaching presence positively influences online learning motivation through social or cognitive presence; (3) factors, such as school location, previous online learning experience, family social-economic status, and prior academic achievements, may influence technology acceptance. The implications for designing, developing, and managing K-12 online education are discussed.