To realize the ejection of heavy projectile with smaller current, a seriesconnected augmented quadruple electromagnetic rail launcher is proposed based on quadruple rail launcher. The mathematics model of electromagnetic thrust generated by the main rails and auxiliary rails of augmented rail launcher is established respectively and the characteristics of electromagnetic thrust are simulated, and a formula of determining the number of rail plies according to preset thrust is given. The ejection process of traditional and augmented rail launcher was modeled and simulated. The results show that the electromagnetic thrust of augmented launcher approaches the maximum at a lower position and the rail current of augmented rail launcher is less than 60％ of the traditional rail launcher when ejecting the projectile to same speed.