The invention provides a data sampling interpolation method. The method comprises the following steps that first, interpolation is carried out, second, different sampling interpolation algorithms are selected, eighty sampling values obtained through ECT sampling and EPT sampling in each cycle can be expanded to obtain two hundred sampling values, and therefore the requirements for carrying out power quality calculation on power quality basic parameters can be met. According to the data sampling interpolation method, data can be sampled in a power quality monitoring device and can be processed, a data receiving end achieves sampling synchronization based on a synchronization scheme of the sampling interpolation algorithms under the premise of not increasing the number of original devices, and the reliability of a system is improved greatly due to the fact that the dependence on synchronizing signals is eliminated.