Target detection is one of important roles of radar systems. In this paper, we present a detection method using total correlation based on information theory for noise radar systems which enables a system detects multiple targets at low signal to noise ratio regimes. The proposed method utilizes the largest eigenvalue of the sample covariance matrix to extract information from replica of the transmitted signal, and can perform better than the conventional total correlation detector when reflected signals have intermediate or low signal to noise ratio. In addition, in order to avoid ambiguous target detection, we find thresholds to guarantee the detection performance with the same receiving antenna elements for a given false alarm probability. The threshold is computed from the largest and smallest eigenvalue distributions based on random matrix theory. Simulations show the proposed detection method can be used for intermediate and low signal to noise ratio environments, and the thresholds provides exact target detection.