Abstract: This paper brings out a method on quantitative software trustworthy evaluation across software development life cycle．First,builds a hierarchical assessment model with decomposition of software trustworthy on the various stages of software development life cycle,designs appropriate quantitative or qualitative metrics set; then,using of knowledge discovery in database techniques to obtain the weights of all software trustworthy characteristics; finally,using of data fusion theory to process and reason large volumes of multi-type measurement data．Engineering practice shows that it can effectively improve objectivity of the assessment process and the accuracy of the assessment results.

Key words: Quantitative evaluation,Software development life cycle (SDLC),Data fusion,Trustworthy,Software engineering