Online learning has become the new educational pattern during the COVID-19 pandemic and is likely to supplement conventional schooling in the post-pandemic world.Lacking prior online learning experiences,the population of K-12 students deserves our special attention.Using purposeful sampling,this study investigated K-12 online learning experiences in China based on a large-scale survey(N=118,589).Leveraging both quantitative and qualitative evidence,this study supported online learning as a flexible alternative to conventional schooling in emergency situations with a discussion of its benefits and limitations,and revealed key findings regarding K-12 students'online learning pattern,experiences,and engagement,as well as the influencing factors.The research findings can inform the future design and implementation of online learning programs in primary and secondary schools.