Abstract: The next generation of synchrotron radiation light sources features extremely low emittance, enabling the generation of synchrotron radiation with significantly higher brilliance, which facilitates the exploration of matter at smaller scales. However, the extremely low emittance results in stronger sextupole magnet strengths, leading to high natural chromaticity. This necessitates the use of sextupole magnets to correct the natural chromaticity. For the Shanghai Synchrotron Radiation Facility Upgrade (SSRF-U), a lattice was designed for the storage ring that can achieve an ultra-low natural emittance of 72.2 pm·rad at the beam energy of 3.5 GeV. However, the significant detuning effects, driven by high second-order resonant driving terms due to strong sextupoles, will degrade the performance of the facility. To resolve this issue, installation of octupoles in the SSRF-U storage ring has been planned. This paper presents the study results on configuration selection and optimization method for the octupoles. An optimal solution for the SSRF-U storage ring was obtained to effectively mitigate the amplitude-dependent tune shift and the second-order chromaticity, consequently leading to an increased dynamic aperture (DA), momentum acceptance (MA), and reduced sensitivity to magnetic field errors.