Lightweight technology application in river-crossing and military bridge equipment has important significance to promote rapid development. Lightweight can efficiently reduce the weight, promote structure optimization and improve performance of the river-crossing and military bridge equipment. After basic principles and main technologies of the lightweight application in the river-crossing and military bridge equipment components are summarized, strength design technologies for the lightweight of the equipment components are discussed, and simple shape components strength design criteria under tension/ compression, bending, shearing and torsion are analyzed, which is extended to general lightweight components strength design criteria. On the basis of the lightweight design principles and strength design criteria, appropriate design methods and optimization strategies are selected, suitable lightweight high-strength material is chosen according to research and development demands, and the lightweight purpose for the river-crossing and military bridge equipment is realized.