Door slit is one of the weakest parts for noise transmission through the door to the outside. It is proposed to apply the active noise control (ANC) technique to reduce noise radiation through door slits in this paper. Numerical simulations are carried out to investigate the performance of the ANC system based on the acoustic transfer functions obtained from a commercial finite element model software. The upper limit frequencies of effective control are discussed and the effect of the primary sound field and absorptive ground on the ANC performance is analyzed.