Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-Ⅱ storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is briefly introduced. Then, the error sources and the optimized measurement method for the HLS-Ⅱ storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-Ⅱ storage ring is less than 1 mm. Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-II storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is uniquely introduced . The error of and the optimized measurement method for the HLS-II storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-II storage ring is less than 1 mm.