One of the main problems in the HCCI engine is the control and operation of the combustion process. At present the primary method of control of the combustion process in an HCCI engine system is EGR (Exhaust Gas Recirculation). The paper presents the results of three-dimensional modeling of combustion in a single-cylinder HCCI engine powered with DMEfuel with a cooled external EGR. 3D modeling was performed in A VL Fire code. This -work investigates the effects of EGR rate on the basic combustion parameters including start of the ignition (SOI), burn duration (BD), indicated pressure (pj and nitric oxide (NO) emissions. The modeling results show that increasing of the EGR rate in HCCI engine can delay the start of ignition (SOI) effectively and leads to a prolongation of the burn duration (BD). Delayed ignition in the HCCI engine through EGR, can provide similar performance (p) compared to conventional CI engine and at the same timeprovide a significant reduction in NOx emissions.