Abstract: Dimethyl ether as fuel for compression ignition engines causes compatibility problem between seal parts and fuel in engine fuel system. The compatibility of seal materials with DME was deeply investigated. Many kinds of rubber materials were chosen to test the expansion, the tensile strength, the tear strength and the hardness. The experimental results show that EPDM has a good resistance to DME; the purity of DME, various lubricant additives and concentrations in DME, different constitutions of EPDM rubber have a certain impact on the resistance of EPDM to DME; and the chosen EPDM has an acceptable volume swelling rate and mechanical performance in a short time when using diesel to adjust highpressure oil pump for fuel DME uniformity in every cylinder.