Line shunts are usually ignored by various power flow (PF) models in distribution system analysis, planning and optimization. However, “charging effects” from line shunts of underground/submarine power cables would cause non-negligible model errors for these commonly used PF models. In this brief, we propose a modified linear Distflow model (LinDist) with line shunts (LinDistS) to address relevant model errors. The strength of the proposed model not only lies in a straightforward structure like LinDist, but also maintaining the linearity after further considering three-phase unbalanced systems. The linearization error of voltage component is theoretically analyzed. Case studies show that compared with non-linear and linear models, LinDistS achieves the descent calculation accuracy and efficiency in large scale distribution systems.