The invention discloses a method for optimizing the transmission line planning scheme for reducing the spatial-temporal distribution of frequency, which selects the optimal line planning scheme. The method comprises steps of formulation of a pre-determined scheme: two or more solutions are provided under the condition that the constraints of the line engineering cost, short-circuit current, and economical operation are met; setting of system disturbance; definition of spatial-temporal distribution indexes: the four spatial-temporal distribution indexes of frequency change rate, response delay,maximum frequency shift, and maximum shift delay are defined; selection of observation points: calculation of evaluation indexes: the observation points are grouped, the mean difference and denormalization of two groups of the spatial-temporal distribution indexes are performed, then weighting and summing are performed to obtain the target value of spatial-temporal distribution under a certain fault, and according to the capacity ratio, different faults are subjected to summing and weighting to obtain the final target value; and selection of the optimal scheme. The method remedies the shortcomings in the spatial-temporal distribution of frequency in the circuit planning and ensures the rationality of the circuit planning.