Technology integration refers to the process of innovation diffusion, from understanding technology knowledge to achieving a high level quality of technology usage. To address the gap in research regarding the critical factors that influence K-12 teachers' practice of technology integration at the initial stage of a massive government-led training programme in rural areas, this study sought to explore the comprehensive effects of teachers' technological pedagogical content knowledge (TPACK) and beliefs on their technology integration. Participants included 267 in-service K-12 teachers from four pilot schools in a remote rural area in north-western China. We found that: (a) T-related knowledge positively predicted the teachers' technology integration quality and quantity, while T-unrelated knowledge negatively influenced technology integration quality and quantity; (b) the positive valence of teachers' beliefs (PVTBs) was positively related to technology integration quality, the negative valence of teachers' beliefs was negatively related to technology integration quantity; (c) the PVTBs impacted the quality and quantity of technology integration through T-related knowledge; and (d) gender significantly moderated the impact of positive beliefs and T-related knowledge on technology integration. This study suggests that improving K-12 teachers' technology integration in rural areas requires prioritizing professional development programmes that improve teachers' beliefs in the initial stage of technology diffusion.