Abstract: Based on π\|type equivalent model of transmission lines, a kind of line estimation method is proposed through magnitude computation by using of SCADA data with measurement of the power flow of both side of the transmission line. Using the data measured from different time sections, the mean value is the final identification result of line parameter by statistic analysis with the set of line parameter. Comparing to the traditional methods, this method has no numerical problems and it works fast and accurately without phase measurement. Taking IEEE\|30 test system as an example, the paper verifies the accuracy of the method.