Provided is a bridge arm digital bridge with a variable phase difference. The invention is a digital bridge of minimalist design. A digital signal processor is used as a core. Standard resistance is switched in a measuring loop so that two phase measurement is performed and thus a measured reactance is obtained. Precision of the bridge only depends on two aspects on principle: standard reactance precision and phase measurement precision so that influence of A/D conversion errors on measuring results can be eliminated and thus relatively precise measurement numerical values are obtained.