The invention provides a power grid operation human factor reliability assessment method and device based on a Bayesian model. The assessment method comprises the steps that root nodes and child nodes of variable factors which are related to the operation behaviors of power grid operation personnel and influence the human factor reliability of power grid operation in the Bayesian model are determined, the prior probability distribution of the root nodes and the contingent probability distribution of the child nodes are determined, and the prior probability distribution of the root nodes is used as the joint probability distribution of father nodes; the joint probability distribution of the father nodes and the contingent probability distribution of the child nodes are sequentially substituted into a formula (please see the specification for the formula) to calculate the joint probability distribution of the child nodes; the joint probability distribution of the child nodes is calculated to be used as the joint probability distribution of the father nodes; the above steps are executed repeatedly until the probability of the human factor reliability of power grid operation is calculated. According to the technical scheme, after a certain operation action is executed by the power grid operation personnel, the human factor reliability of power grid operation of the operation action can be quantized.