Abstract: With the increase of distributed energy and energy storage capacity and the popularization of electric vehicles, the power flow in the distribution network has changed from unidirectional to bidirectional, and the network topology has changed from a radial structure to a complex meshed structure. In order to efficiently deal with the power flow (PF) analysis and optimal PF (OPF) problems of meshed distribution networks, as well as to further improve the approximation accuracy of the existing linearization models and to refine the linear approximation of network losses, this paper constructs an iterative implicit linearization PF model (IIL-PF) and its optimal PF model (IIL-OPF). The proposed model considers the nonlinear PF manifold \mathcalM as an implicit algebraic relationship between the node voltages and the nodal power injections, after which \mathcalM is locally approximated using the tangent plane, and the linearization points are iteratively updated to improve the approximation accuracy of the linear model. In addition, the proposed model considers the branch start/end PF, the squared PF, and the line losses, and derives an explicit linearization for them. Finally, based on the modified IEEE 33 system in radial and meshed operation modes, respectively, it is verified that the proposed model can converge quickly and has high approximation accuracy. The results of IIL-PF, objective function of IIL-OPF and generator power are within 1% error compared with MATPOWER's nonlinear models, so the proposed model can meet the requirements of engineering planning or day-ahead operation simulation.