In recent years, integrated circuits subject to hardware Trojans attack in the design and manufacturing process, the security of chip and hardware security was threatened. Some detection methods of have been proposed, the most common of those methods is based on side-channel signal analysis, however, since the effect of process noise, considering only the unilateral information that is difficult to effectively distinguish the noise and Trojans circuit. In this paper, the method still based on side-channel signal, but it is a combination of power and delay which was called the power-delay product (PDP). The idea proposed is verified by the benchmark circuit iscas85, the experimental results show that this method can effectively improve detection probability.