Abstract—Software is everywhere. However, software is not always trustworthy. Confronting the demand of software trustworthiness evaluation, this paper proposes a novel software trustworthiness evaluation approach based on combination weights (CW) and improved TOPSIS methods. The determination of CW relies on experts' judgment and mathematical computation together. FAHP method is used to determine the importance of degree of criteria accordingexperts'judgment. To avoid the subjective onesidedness of weights, entropy weighting method is employed to calculate objective weights. Then, the paper adopts combination weighting method to obtain the CW of evaluation criterion. Next, the CW is applied to the improved TOPSIS method and the trustworthiness rating of software is calculated. The result contributes to provide decision makers more decision information. Finally, the proposed approach is demonstrated with the evaluation of PLM software for an aircraft equipment manufacturer in China, which is followed by the sensitivity analysis and the results illustrate the robustness of the presented evaluation approach.