In order to improve the accuracy of passive localization,a localization algorithm using the Time Difference of Arrival (TDOA) and Gain Ratio of Arrival (GROA) measurements is proposed based on Constrained Total Least-Square algorithm (CTLS).Firstly,a pseudo linear equation is established by using TDOA/GROA measurements.Taking the correlation of coefficient noise in pseudo linear equation into consideration,CTLS method is used for modeling,Lagrange multipliers together with the Newton iterative method are used for solution.Simulation results show that: 1) When the noise is relatively low,the proposed method approximates the lower limit of CRLB; 2) When the noise is higher,the proposed method offers better localization accuracy compared with the two-step WLS method; and 3) With the increase of parameter c/w,the localization mean square error of this proposed algorithm is also less than that of the two-step WLS method.