Whether correlators can output correlation peak is the main way to determine the target authenticity of correlators. However, it is prone to misjudgment when the accuracy of the components adjustment is not high enough. Based on the matched filtering correlators, we make theoretical analysis of three cases about the misjudgment of the correlation peaks. We give special emphasis to the theoretical and experimental study on correlation signal strength discrimination. Considering the three cases about the misjudgment of the correlation peaks, we explore the judgment of correlation peaks from the threshold intensity and the form of the correlation peaks, and the angle of rotation of the input image, which provide reference for experimental determination of the correlation peak.