This dataset contains inclination, corrected declination, and relative paleointensity (RPI) data from sediment core BKAS58PC, spanning the past 30 ka. The core was retrieved from the Beikang Ansha area in the southern South China Sea (SCS) using a gravity corer during the HYDZ4 cruise in 2014. The chronology of BKAS58PC was established based on 16 radiocarbon dates using Bacon program. Natural remanent magnetization (NRM) and stepwise alternating field (AF) demagnetization were performed using a 2G-760 superconducting rock magnetometer with peak magnetic fields ranging from 0 to 80 mT and steps of 10 mT. The inclination and declination data were obtained using principal component analysis of NRM demagnetization results, with at least five demagnetization steps used to isolate the characteristic remanent magnetization. Since the core was not azimuthally oriented during sampling, the declination was corrected by aligning the mean declination of the top three samples to the modern geomagnetic field direction. Relative paleointensity was estimated using the difference in the NRM versus saturation isothermal remanent magnetization ratio within the 20–50 mT demagnetization interval. The dataset provides high-resolution records of geomagnetic field variations in the southern SCS, contributing to regional and global paleomagnetic reconstructions.