Abstract: In recent years, with the rapid development of aerospace technology, the functions of aerospace software are becoming more and more complex and the scale is getting lager while the requirements for software trustworthiness are getting further. Once aerospace software is untrustworthy, the loss it brings is often incalculable. We propose an approach for software trustworthiness measurement for aerospace, starting from the trustworthy evidence of source code in combination with the characteristics of aerospace. We design a trustworthy evidence standard for C Language which distinguishes key evidence from the evidence and includes positive evidence and negative evidence. Then, we propose an approach of aerospace software trustworthiness measurement oriented to trustworthy evidence of source code and a software trustworthy classification model. Finally, we use the approach to measure the trustworthiness of NASA’s open source code Core Flight Executive, and the result proves the effectiveness and practicality of our approach.