Correlation Interferometer is a passive direction finding algorithm, which has the characteristics of low computational complexity, strong anti-interference ability and sample’s environment dependence. In order to reduce the dependence of the sample on the environment and improve the accuracy in actual working environment, an improved algorithm based on theoretical samples is proposed in this paper. By searching the local peak value of correlation matrix, establishing theoretical correlation peak system, calculating correlation peak evaluation coefficient ( including variance, kurtosis, skewness), and quadratic correlation matching, the algorithm can accurately detect the direction of arrival signal with theoretical samples. Field experiments show that in the frequency band 340 MHz~ 3 GHz and the signal-to-noise ratio 29 ~ 60 dB, the accuracy of the improved algorithm is 0. 8° higher than that of the traditional sampling algorithm in the urban environment. At the same time, the overall accuracy difference of many experiments is less than 1°. The improved algorithm has high computational complexity, and the cost of time is 3~ 4 times that of the traditional algorithm, and it has good practical value in scenarios without high timeliness requirements.