The invention discloses a risk assessment and analysis method based on power grid short-time run-time behaviors. The method includes the following steps that risk assessment of a power grid short-time operation state is described, and decision quantity and constraint conditions are selected; on the basis of equipment state monitoring, equipment fault rate prediction and power use demand rules of nodes of a power grid, a sample set is generated, a power grid risk assessment model is built, a time domain mode is simplified; and correlated constraints are decoupled; an objective function of each scene sub-cycle is built, the constraint conditions are calculated, and the minimum cost function in a cycle is solved; the power grid risk assessment model is solved, and an assessment result is analyzed. According to the method, in long-term decision behavior process such as overhaul, it is necessary to take the power grid short-time run-time behaviors into consideration, and economical performance and reliability of decision schemes can be greatly improved through coordination and decision-making of the method and the power grid short-time run-time behaviors.