Abstract: A lexicographic ordermultiobjectandmultistage decisionmodelwas derived. The principle and algorithm of Jar-metricwere applied to solving the problem. In a Jar-metric graph representing a lexicographic ordermultiobject andmultistage decision problem, a Jar valve from a starting node to a destination node is equal to a monoid sum from the starting node to the destination node, and the monoid sum is independentof the nodes before the starting one and those after the destination one. In the calculation, conjunction is taken as Jar summation, and ordinary summation is regarded asmonoid produc.t In this way, the recursive calculation for solving lexicographic order multiobject and multistage decision problem is transformed to amultistage Jarmatrix computation.