The invention relates to a network type expense estimating system based on a three-dimensional factory model, which belongs to the technical field of computer application. The expense estimating system comprises a central server, a communication network, at least one three-dimensional design and expense estimating dual-purpose workstation and at least one engineering decision workstation, wherein the central server at least comprises one three-dimensional design module basic database, an engineering change order database, a material expense estimating database and an E-mail sender; and the central server, the three-dimensional design and expense estimating dual-purpose workstation and the engineering decision workstation are connected into a whole through the communication network. According to the invention, engineering designers can quickly estimate material quantity and installation engineering quantity required for engineering during three-dimensional modeling, and can also screen out the set of optimal design plans with the cost in a budget range; and engineering change orders and the set of the optimal plans are sent to deciders through a network communication system for approval or selection.