Crankshaft is the most important and hard manufacture part in engine and diesel, its deformation contains multiple arcs, and its straightening technology is a complex NP-hard determination problem. The crankshaft straightening process was analyzed, and some effects from multiple arcs crankshaft straightening was investigated. The mathematics model of multiple arcs straightening technology determination system was built based on graph theory principle. And the Influence of Bauschinger effect was considered, the online straightening technology determination calculation algorithm based on weighted evaluation function was proposed. The experiments about straightening crankshaft were performed in YH40-160 straightening press to evaluate two different weighted set C1={2.5,1.5,1,1.2,3.5} and C2={1,1,1,1,1}, and the results expressed that the online straightening technology determination calculation algorithm was advantage to crankshaft straightening process, and C1 had better influence to qualities and efficiencies than C2.