To predict the mechanical response of IN718 alloy under various complex conditions accurately and reliably, the theoretical modeling of serrated plasticity of microsized single-crystal IN718 alloy under displacement control was carried out. Starting from the micro-compression test, a simple deformable body-spring model was proposed to further elucidate the serrated plasticity under the displacement control. Subsequently, the independent modeling elements such as strain hardening, flow rule, loading-unloading criterion, and strain burst criterion were taken into consideration. Then, a continuum constitutive model for the serrated plasticity was established. This model was used to study the compression response of IN718 micropillars with single slip and double slip orientation, respectively. The simulations produced clearly a series of visible strain bursts, loading and unloading process in micropillar plasticity, and the exhibited serrated flows are comparable with the corresponding experimental observations. The proposed continuum model for the serrated plasticity can provide a strong theoretical support for the development of the classical crystal plasticity theory in the sub-micron scale.