When an abnormal precipitation record from a regional automatic weather station appears unusually high or historically significant, or greatly larger those of the neighboring stations, the conventional data quality control (QC) method will generally judge it as a suspected case. In this paper, the onsite check method for the situation is described, including the start of the check, the sensor error and instrument performance checking, the assessment of detection environment, and other procedures such as conclusion making and final report forming. An example is used to test the effectiveness and applicability of this method.