The research of extracting periodic signals is of great value in the field such as medicine. A precise estimation for period of target signals with priori knowledge is necessary in such kind of algorithms. But most of algorithms are sensitive to the error from the estimation. The algorithm proposed in the article including steps as follows: first roughly evaluate the extracting matrix with the improved time domain correlation function by evaluating the existing interval of optimizing time delay, use negentropy as the target function with the correlation function given into consideration to ensure the order and optimize it with Newton iterative method. The simulation and the experiment with real ECG data prove that the proposed algorithm can get a better result in the extraction than other algorithms, and show its robustness to the error of time delay.