A calibration technique for time domain reflectometry and transmission (TDR and TDT) measurement system as applied to network analysis is presented. The calibration corrects for the errors caused by the response of the measurement system. A complete physically-based model has been established for the system. A set of calculable standards has been developed to satisfy the time domain requirements for calibration. The calibration technique was applied to determining the model parameters of a commercial TDR and TDT system. The errors of modeling and de-embedding are analyzed. The calibration enhanced the system bandwidth from 8 GHz to about 20 GHz. Experimental verification is given to demonstrate the validity and accuracy of the calibration technique.