The uniformity measuring function of the uniformly-distributed transmission power grid diagram is presented and a mathematical optimization model is given，but the model is hardly solvable by general optimization methods.Therefore，a novel force-direction algorithm is developed to overcome the drawback of existing force-direction algorithms which has the following three procedures:（1）the Bary-centralization algorithm is adopted to have a fast initial layout;（2）based on the F&R algorithm，weight coefficients are added for gravitational force calculation of different voltage lines;（3）the gravity coefficient is introduced to the node movement correction equations to avoid the problem of most force-direction algorithm that the node distribution trend to the edge of the diagram in the network of large numbers of nodes，and comparisons of this algorithm with other existing force-direction algorithms are given.This algorithm is applied to the automatic generation of a provincial transmission power grid diagram，and the comparison of this algorithm with similar algorithms at home and abroad prove that this algorithm has a fast calculation speed，and the automatically generated transmission power grid diagram has less intersections，clean diagrams and a uniform distribution.