Abstract: Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation light source that has been operating steadily and consistently providing high brightness X-rays to multidisciplinary fields for over a decade. This achievement is mainly attributed to the long-term stability of electron beam parameters, among them, the linear optical model is the most important to guarantee the stability of light source properties and the stable operation. The brightness of synchrotron radiation, beam emittance, beam lifetime and other important parameters are directly affected by the linear optical functions. In SSRF, the tune feedback system based on the response matrix method was tested in the first half of 2019 and then put into operation during normal user time. This feedback system can not only correct the betatron tunes online, but also realize the dimension reduction correction of linear optical functions. The stable operation of the tune feedback system in SSRF has proved the feasibility of this method. The results of operation in several weeks show that the feedback system not only significantly improves the stability of the tunes, but also improves the stability of important beam parameters such as beam emittance, injection efficiency and beam lifetime. In addition, diffraction-limited storage ring (DLSR) light sources with higher brightness and transverse coherence are being widely studied and constructed worldwide. The round beam mode based on linear difference coupling resonance will be used by some DLSR facilities to optimize the matching of photon and electron beams in phase space and to improve the beam lifetime. The stable operation of this kind of round beam mode highly requires the stability of betatron tunes. Therefore, it is very important to improve the stability of betatron tunes for the stable operation of the third-generation synchrotron radiation light sources and more important for DLSRs. The feasibility of the tune feedback system on the new generation of light sources needs to be verified. For this purpose, the tune feedback system on the SSRF-U storage ring lattice was simulated, where SSRF-U is an important alternative for upgrading SSRF to diffraction-limited storage ring with an extremely low natural emittance of 53.2 pm·rad. The simulation results show that the tune stability of SSRF-U is better than ±0.001 under the action of the tune feedback. Such a high tune stability is enough to meet the needs of the linear difference coupling resonance round beam mode in DLSRs for the stability operation. In summary, this paper analyses the principle of tune feedback, reviews the operation of SSRF tune feedback system, and introduces the simulation of tune feedback on SSRF-U.