Abstract: The increasing number of the Internet of things (IoT) devices in our environment presents significant opportunities as well as challenges, including limited battery life, low computing power, and scalability for multiple access. Recent advances in backscatter communication have enabled ubiquitous IoT devices to communicate in an energy-effective manner. However, a fundamental challenge in backscatter communication is to design a multiple access protocol to support concurrent communications from numerous tags. Aiming at tackling the high bit error rate and low transmission rate of large-scale tag concurrent communication, we design a coding-based code division multiple access technique to facilitate multi-tag backscattering with reliable communication. Firstly, the chip discrimination tags with strong orthogonality such as Walsh code are combined with error correction coding to enhance the anti-interference ability. Secondly, the joint decoding of correlation detection and decoding is used to reduce the bit error rate and realize the reliable communication from the backscatter link. Finally, a grouping algorithm is designed to cluster tags based on the K-means clustering algorithm, which fully utilizes the time-code resources and enhances the capacity. Experimental results demonstrate that our scheme can achieve reliable communication with 100+ tags, with a bit error rate of approximately 2%, and the achieved throughput of 39 Mbps.