Abstract: Because of OTHR long rang,and it suffers the influence of ionosphere severity,if we evaluate the ability of the OTHR with the old range measuring method used in common radar,it will cause a lot of waste.Due to this problem,a method of modeling RCS by transponder beacon is proposed,and an analysis of the simulated RCS accuracy was carried out.A calibration method for this kind of method is proposed.Theory and practice all show that this calibration method is viable.Because of the tran- sponder beacon's flexibility and simplicity,it can work well for the evaluating experimentation of OTHR.