Oblate spherical propellant is the main charges for small and medium caliber and light weapons， and the method of controlling its progressive properties has consistently been a hot research topic. The ethyl cellulose （EC）-coated microporous gun propellant was developed by combining internal microporous combustion enhancement using SC-CO₂ and the surface coating flame retardant via fluidized bed coating， resulting in precise and controllable energy release. Scanning electron microscopy and infrared spectroscopy were applied to investigate the microstructure and composition， and the closed bomb device was used to analyze the combustion and storage performance. The results showed that the coated microporous gun propellant exhibited surface structural integrity and density. The mass fraction of the coating layer increased from 2.32% to 9.79% when the coating time was increased from 5 min to 30 min， and the corresponding film thickness increased from 7 μm to 33 μm. Compared with the original gun propellant， the initial and maximum activities L₀ and L_m of the microporous gun propellant with 10 min coating time were reduced by 62.34% and 55.61%， respectively， with an A_L-B characteristic value of 1.304 MPa^-1·s^-1. Accelerated aging tests showed minimal changes in the combustion performance of the coated spherical propellant. The p-t and L-B curves of the aged samples were consistent with those of the untreated samples after aging at 75 ℃ for 14 days. This indicated that the EC-coated microporous gun propellant exhibits excellent storage stability.