The invention provides a data compression iterative calculation method based on principal component analysis, which is used for solving the problem of large calculation amount caused by the fact thata principal component analysis method is adopted to compress the measurement data of an electric power system in the prior art. Based on the principal component analysis and calculation method for data compression, through iterative computation, a feature vector matrix of previous principal component analysis data compression is used to approximately serve as a feature vector matrix of current data compression for current data compression, and whether the current compression can approximately use the previous feature vector matrix or not is judged under the condition that the precision of reconstructed data is judged. According to the method, the same characteristics of the original data can be extracted without a large data window, and the data compression efficiency and real-time performance can be remarkably improved; and meanwhile, the strong correlation and the relationship consistency between the measurement data of the power system are fully utilized, so that a principal component analysis data compression algorithm is calculated only once again when the disturbance occurs and once again when the disturbance ends, and the calculated amount is remarkably reduced.