Benefiting from high volumetric energy density and generally dendrite-free growth of Mg metal, rechargeable magnesium batteries (MBs) become a promising next-generation energy storage system. Organic electrode materials, with characteristic of sustainable resource and flexible structure, have been widely studied in alkali metal ion batteries, but are rarely reported in MBs. Herein, we demonstrate that 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) serves as a cathode material for MBs in non-aqueous system, which realizes a fast diffusion kinetics and remarkable Mg-storage performance through a salt-dissolution inhibition approach for the electrolyte. The PTCDA exhibits a reversible capacity of 126 mAh g−1 (at 200 mA g−1), excellent rate performance, and good cycling stability (100 mAh g−1 even after 150 cycles). Furthermore, the evolution mechanism of the PTCDA electrode based on the transformation between carbonyl groups (CO) and enolate groups (C–O) is revealed by ex-situ phase characterization and functional group analysis. Besides, the dissolution inhibition of the PTCDA could also be realized through the incorporation of other soluble salt (KCl or NaCl) into all phenyl complex (APC) electrolyte, resulting in an enhanced cycling capacity. Considering the designable configuration of the organic materials, this work would pave way for their utilization on multi-valent ion batteries and provide efficient strategy to realize high voltage and satisfied cycle life.