In order to reduce the measurement error of the unbalanced bridge，a method based on the particle swarm algorithm to control the uncertainty of the unbalanced bridge was proposed． First，the uncertainty evaluation model of the unbalanced bridge was established，and then the particle swarm algorithm was used to optimize the various influencing parameters．Finally，the comparison experiment of the uncertainty before and after the algorithm optimization was carried out．The results showed that the method of this paper can reduce the uncertainty of the unbalanced bridge measurement by 98． 64%，and could be applied to various teaching experiments that need resistance．