Abstract: This paper discusses the drifts of monitoring EDM parameters by the way of rank-defect freenetwork adjustment.In the first place,it is proved that the adjustment of monitoring EDM parameters with the combinatorial method is a problem of rank-defect adjustment.After that,two ways of adjustment are discussed,the tests of significant drifts of parameters are studied and several examples are given.The conclusion is drawn that these methods will be effective in monitoring EDM parameter drifts and reducing the test costs to baseline site for the special purpose if we pay sufficient attention to advancing the monitoring accuracy.