With the widespread application of microgrids, a number of adjacent microgrids in a certain area will form multi‐microgrids (MMGs) with three‐phase/single‐phase (TP/SP) architecture. Owing to the complicated structure and the various operation modes of MMGs, it is an urgent problem that how to achieve seamless handoff between multiple operation modes in the MMGs. Based on the analysis of the topology of MMGs with TP/SP architecture and the hierarchical control architecture, this study proposes the islanding partition method algorithm correspondingly. The discrete particle swarm optimisation algorithm is proposed to solve the problem by establishing the comprehensive evaluation of islanding MMGs with TP/SP architecture, which can effectively solve the problem of dimension explosion when the number of microgrids increases. The results of simulation show the applicability of the proposed strategy for MMGs.