The hydrosilylation reaction of ethylene with triethoxysilane catalyzed by ruthenium halides and promoted by cuprous halides, iodine or ferrous chloride tetrahydrates was conducted at temperatures ranging from 30 to 80 °C under a mild pressure of ethylene gas. Ruthenium chloride trihydrates and cuprous chloride are proved to be the best catalyst and promoter for this reaction. With the addition of 6.8 × 10 −5 mol ruthenium chloride trihydrates per mole of triethoxysilane together with over 3 times of cuprous chloride per mole of ruthenium chloride trihydrates, the reaction can conduct rapidly at temperatures ranging from 40 to 60 °C under a pressure of ethylene gas lower than 0.35 MPa with over 96% yield of ethyltriethoxysilane within 6 h.