Abstract Three-dimensional numerical models of bedded rock salt cavern gas storages of Jintan salt mine, Jiangsu province, China, are established using FLAC 3D simulator to investigate factors affecting the allowable width for pillars between two adjacent caverns. Vertical stress, deformation, plastic zone, safety factors, and seepage pressure of pillars between two adjacent salt caverns are discussed, and the allowable width of the pillars is optimized. Results show that the vertical stress on the pillars increases with depth and decreases with increasing pillar width, gas pressure inside the caverns, and creep time, i.e., cavern operating duration. Rock salt creep gradually smoothens the vertical stresses on the pillars, and the effect is expected to become imperceptible after five years. An increase in gas pressure difference between the caverns increases shear stresses in the pillars, which aggravates the unevenness of stress distributions and reduces the stability of the pillars. The asynchronous injection–production mode has negative effects on pillar stability and seepage pressure, particularly for narrow pillars. Interlayer permeability and pillar width are key factors affecting seepage through the pillars. The allowable pillar width for bedded salt cavern gas storage groups in Jintan salt mine, Jiangsu province, China, is proposed based on vertical stress, deformation, plastic zone, safety factors, and seepage pressure, and is recommended to be 2.0–2.5 times the maximum diameter of a cavern. This is a smaller range than the pillar width proposed by available codes, which ranges from 1.5 to 3.0 times the maximum diameter of a cavern. This decreases the uncertainty in the pillar width design caused by the conventional wide range and can increase the efficient use of the rock salt resources. The study provides fundamental data and references for designing pillars for salt cavern gas storages in other areas with similar conditions.