This paper proposes a novel multi-reader joint detection scheme for dense Radio Frequency Identification(RFID) networks to reduce interference among multiple readers and tags and improve network capacity. By deploying RFID reader in high density and applying the Interleave Division Multiple Access(IDMA) scheme, signals from multiple tags can be resolved. This allows joint detection and diversity combining among different readers，resulting in better channel reuse. Through computer simulations，it is shown that the proposed system can achieve channel multiplexing by around 2-6 times with equal or better BER in dense RFID environment.