Internet of Things (IoT) is an emerging network technology applied to provide various services in our daily life. Generally, IoT environments are composed of numerous heterogeneous devices with constrained resource. The limited capability of IoT devices makes it impractical to perform traditional security mechanisms, and thus IoT services are usually vulnerable to all kinds of security threats, such as impersonation and forgery attacks. Moreover, the inflexible protection provided by these security mechanisms leads to inefficiency because different services haves diverse requirements. To provide IoT services suitable security protection, Multi-graph Zero-knowledge-based Authentication System (M-ZAS), which is not only light-weight but also high-adaptive, is proposed. Compared to traditional authentication mechanisms as well as other Zero-knowledge-proof (ZKP) methods such as GMW-ZKP, M-ZAS provides higher performance and better security protection. In addition, M-ZAS has lower transmission overheads than GMW-ZKP does. Considering relevant contexts as parameters, M-ZAS provides adaptive protection to fulfill what users actually need. Experiment results show that M-ZAS is 3 times faster than GMW-ZKP and even 7 times than traditional authentication mechanisms in IoT devices. Also, M-ZAS reduces 3 times network traffic than GMW-ZKP. Thus, the proposed M-ZAS is the most practical authentication system in IoT environments.