To study the influence rule of afterburning effect on the parameters of explosion field, a numerical calculation method for the explosion field in a closed space considering the afterburning effects was proposed. The simplified reaction rate model was coupled with three-dimensional two components compressible Euler equations to approximately consider afterburning effects. Transient temperature was obtained by establishing the relationship between gas internal energy and heat capacity. The calculation formula of specific heat ratio was established according to thermodynamic relation. Based on FORTRAN platform, the fifth-order WENO finite difference scheme was adopted to develop an in-house 3D numerical calculation code, which can simulate the explosion field in closed space considering afterburning effects. The evolution process of internal explosion field and the influence of afterburning effects on the calculated explosion field parameters were numerically discussed based on the developed code. Results show that （1）the numerical solutions of quasi-static temperature, specific heat ratio and overpressure are in good agreement with theoretical solutions considering afterburning effects, and the relative error is less than 5%. The reliability of the developed code is preliminarily verified. （2）the afterburning effects should be paid enough attention in numerical simulation of internal explosion field. Under the same internal explosion condition, the relative errors between the numerical solutions of quasi-static temperature, specific heat ratio and overpressure and theoretical solutions without considering afterburning effects are as high as 25%, 6% and 31%, respectively, This research method can be applied to the numerical calculation of internal explosion of other types of explosives, and provide some reference and guidance for the evaluation of internal explosion damage