In analog circuit design, the zero drift is a special problem of direct coupling amplifier circuit. Combining with engineering application cases, the paper introduces the problems caused by amplifier AD620 instrument zero drift, points out its forming reason, and analyzes the influence. Through the selection of different filer capacitances, it concludes the influence of the common-mode rejection ratio on the zero drift. This article can offer reference for the actual possible acquisition to avoid the issues such as difference of ultra-precision, and provide some reference and basis for fault analysis.