The invention relates to an evaluation method considering influence of new energy grid connection on the utilization rate of transmission network. The evaluation method comprises that a photovoltaic output probability model considering influence of illumination randomness is established; a wind power output probability model considering influence of wind speed randomness is established; a load probability distribution model and a generator outage probability model are established; the trend probability distribution of lines and transformer with and without new energy is calculated respectively in a Monte Carlo probability trend method; a transmission network utilization rate index system considering the operation characteristic is defined; and the utilization rate of the transmission network is calculated via the transmission network utilization rate index system, the utilization rate indexes of the transmission network with and without new energy are compared, and influence of new energy grid connection on the utilization rate of the transmission network is obtained. The evaluation method can be used to reflect the real capacity utilization condition of lines in future, search weak links and unreasonable rack structures in the electrical network system, evaluate the utilization state of the future electrical network more accurately, and consider the influence of new energy grid connection in a concise and effective manner.