In view of the contradiction between equipment technology upgrading and cost control, a method of equipment life-cycle cost management and control based on digital transformation is proposed. From the perspective of equipment life cycle, this paper analyzes the risk of cost out of control faced by equipment R & D, production, maintenance and other links in digital transformation, and discusses the comprehensive solution based on target cost method, parameter model method and intelligent technology. The dual objectives of equipment performance improvement and cost optimization can be achieved by building a full-chain cost digital twin system, implementing dynamic cost control based on performance parameters, and strengthening data-driven decision-making mechanism. The case study of a certain country's defense acquisition experience and domestic practice shows that this method can accurately locate the direction of cost optimization, and provide strong support for the dynamic matching of equipment function and cost.