When the signal frequency locates in the area near the midpoint of two neighboring discrete frequencies, the performance of IIN algorithm is poor. But when the signal frequency is near the discrete frequency, the performance of Rife algorithm is poor. A new algorithm called R-IIN algorithm is presented. Firstly, the signal frequency is approximately estimated using Rife algorithm.Secondly, move the signal frequency to the area near the discrete frequency. Finally, the frequency is estimated by IIN algorithm. Simulation results show the performance of R-IIN is better than M-Rife[4] and one iteration of IIN[8] algorithm, and close to IIN of two iterations.