Abstract: Aiming at the potential change caused by chloride leakage of Ag/AgCl reference electrode in in-situ soil monitoring, a flexible Ag/AgCl reference electrode modified with liquid metal fiber mat was prepared. The influence of preparation parameters of liquid metal fiber mat on the potential stability of the reference electrode was studied and the parameters were optimized. In order to improve the stability（reduce the standard deviation（s））, one solution parameter and four process parameters were selected for single factor test. Finally, three key factors were selected, namely the mass ratio of polystyrene（styrene-block-butadiene-block-styrene）（SBS） to 1, 2-dichloroethane, the collection distance of electrospun fibers and the number of tension required for activation electrode. Then based on Box-Behnken principle, the 3-factor and 3-level response surface optimization experiments were carried out. The results showed that the order of influence was as follows: collection distance, mass ratio and drawing numbers. The coupling effect of collection distance and drawing number was significant. When the mass ratio was 1∶5, the collection distance was 19 cm, and the drawing number was 1 150 times, the model prediction results were better, and the average relative error of the verification set was no more than 4.4%, indicating that the parameter optimization model was reliable. In addition, the flexible Ag/AgCl reference electrode was prepared based on the optimal parameters and applied to the soil column nitrate nitrogen and pH monitoring test. The absolute error between the nitrate nitrogen detection results and the commercial electrode measurements was less than 5.55 mg/L, the relative error was less than 7.2%, and the root-mean-square error was 1.98 mg/L. The absolute and relative errors between the pH test results and the commercial electrode measurements were less than 0.21, less than 2.8%, and the root-mean-square error was only 0.17. At the same time, the data of the two groups of flexible electrodes were consistent with that of commercial electrodes.