Abstract: It is the condition necessary to obtain global optimal solution that the object function satisfies convex or at least unimodal curve property when nonlinear programming method is utilized to implement optimization analysis. Several curves of object function about oil transporting optimization for pipeline are obtained by use of numerical method. The discussion is made on their characteristic in given searching domain to investigate whether they satisfy the condition above and which measures should be taken to avoid global optimal solution loss in analysis process if they were not satisfied. The results show that these curves all have the feature of multimodal distribution and generally do not satisfy above condition. This demonstrates that there is a great possibility that only local optimal solution would be obtained if available measure were not be taken when using nonlinear programming method to search optimal transportation scheme for oil pipe-line. Thus several measures are outlined in this paper. The inherence of any measure among them is to find smaller zone before optimizing process, in which not only it is the global optimal solution situated but also the above condition could be satisfied.