The invention relates to a line connection system for three-dimensional design of power transformation engineering electrical equipment. The system comprises: a model line function module which is used for creating a model line of a path, and carrying out the change, combination and grouping of the created model line; a lofting function module which is used for generating a lofting model from thecreated model line and changing the generated lofting model; and an auxiliary function module which is used for setting fittings, supports and space marks in the three-dimensional model and combiningand decomposing families. Compared with the prior art, the method has the advantages of being convenient for project maintenance, easy to manage, capable of improving the design efficiency and the like.