In this paper, we designed a dual-beam external differential interference eye-axis detection system with the Twyman-Green interferometric system architecture combined with digital signal processing technology to achieve low-coherence optical eye-axis length measurement. We implemented multiple measurements of the ZEISS standard analog eye axis and the human eye axis under the same conditions, the results showed that the eye-axis length measurement system designed in this paper had good validity and reliability. However, this system still had the error caused by the cooperation between the operator and the test subject during measurement, so we set the signal-to-noise ratio to >2.3 to ignore the interference of noise in the signal. In the next study, we will continue to optimize the signal processing method to improve the signal-to-noise ratio to enhance the accuracy of the measurements. This is necessary for accurate prediction of early pseudomyopia and myopia, their prevention and control, and to provide a technical solution for domestic AL measurement.