The invention discloses a smart distribution network risk assessment method considering the rationality of network topology. The method comprises steps of setting a fault probability diagnosis module,setting a network topology rationality evaluation module and determining a real-time risk value of a power distribution system. With real-time prevention control as a target, a risk index is selectedand a quantization scheme is designed in aspects of the fault probability of the main equipment of the distribution network and the rationality of the network topology structure; all levels of indexweights are made in a unified manner by using an analytic hierarchy process; and the risk degree of the distribution network operation is comprehensively evaluated. According to the invention, the assessment of the risk operation state of the distribution network system is perfected by identifying severity of the fault consequences under different network topologies; and thus the frequency of fault occurrence of the distribution network and the severity of the fault consequences are considered comprehensively to obtain the real-time risk value of the distribution network, thereby providing guidance for the subsequent control measures, avoiding the high-risk equipment and strengthening the ability of the distribution network against the faults.