Low elevation estimation,which has attracted wide attention due to the presence of specular multipath,is essential for tracking radars.Frequency agility not only has the advantage of strong anti-interference ability,but also can enhance the per-formance of tracking radars.A frequency-agile refined maxi-mum likelihood(RML)algorithm based on optimal fusion is pro-posed.The algorithm constructs an optimization problem,which minimizes the mean square error(MSE)of angle estimation.Thereby,the optimal weight at different frequency points is ob-tained for fusing the angle estimation.Through theoretical ana-lysis and simulation,the frequency-agile RML algorithm based on optimal fusion can improve the accuracy of angle estimation effectively.