Wireless Sensor Network is a collection of many sensor nodes and is more vulnerable to node replica attack. Among many physical attacks to sensor networks, the node clone is a serious and dangerous one because sensor nodes are generally short of tamper-resistance hardware components. An adversary can capture few nodes, extract code and all secret information to replica many nodes. That replica nodes act as a original node, and can freely enter the sensor network and then extend the adversary's capacities to perform the network maliciously and have whole control over the network. In the existing system, even though private keys are used for both identity and location of the sensor node, still the nodes are compromised by the attacker and also those methods are based on centralized system, and it increases communication burden and increases complexity to detect the clone node. To overcome these problems, two detection algorithms are proposed. Distributed Hash Table (DHT) is a decentralized, key-based caching and checking system to detect the clone node. DHT-based detection algorithm can use chord overlay network to detect node clone with high security level. Randomly Directed Exploration (RDE), a distributed system providing good communication performance, uses two methods probabilistic directed forwarding with random initial direction and border determination for detecting the clone node. RDE has high detection probability compared to DHT-based detection algorithms.