The signal detection method of stress-strain sensing system based on the principle of Brillouin backscattering is studied. At present, the signal detection method in this field generally has many problems, such as large amount of calculation, low accuracy, and poor consistency. This paper proposes an adaptive gradient descent algorithm (Adam algorithm), which can be used to fit the Brillouin scattering signal. Meanwhile, a Brillouin strain measurement system for heterodyne coherent detection is established. Experimental results show that the average strain error demodulated after fitting the scattering spectrum curve with the Adam algorithm is 24. 89 με, which is 51. 96% of the maximum strain error of the Gauss-Newton algorithm fitting curve. This value is Levenberg-Marquardt LM algorithm fits 57. 42% of the maximum strain error of the curve. When Adam algorithm is used to fit the scattering spectrum curve, the good fit is 0. 998 9 and small root mean square error is 0. 110 5. These results indicate high precision of fitting measurement and signal processing. In addition, the signal processing time is only 18. 5 ms. Research results of this study provide theoretical and experimental basis for the high-precision data feature extraction of Brillouin scattering sensing technology.