Phthalates, which often have to be used as deterrents during gun propellants production for realizing progressive burning, are widely believed to be harmful to human and the environment. Meanwhile, phthalates also generate much smoke during propellant combustion, thus, lowering firing accuracy and exposing positions, which may bring risk. To avoid phthalates usage during propellants production, this work, for the first time, reported the employment of "gradient denitration" strategy to prepare nitrocellulose-based gun propellant without the addition of any phthalate deterrents. The successful preparation of gradiently denitrated gun propellant (GDGP) was supported by FT-IR, Raman spectroscopy and FESEM equipped with energy-dispersive X-ray spectroscopy (EDS), as evidenced by the gradiently increased content of nitrogen and nitrate group from the surface to the core of GDGP. Such a denitration process, without any hazardous phthalates deterrents addition, could also realize the good progressive burning performance of the gun propellant, as confirmed by closed bomb test and ballistic gun test. Meanwhile, both theoretical calculation and weapon muzzle smoke test also demonstrated the lowering of smoke generation during propellant combustion. This phthalates-free strategy paves a new way to eliminate potential hazards associated with phthalates during traditional gun propellant production and application.