Abstract: How to evaluate software objectively and exactly is a most important subject. `baking advantage of our expe rience in software testing and evaluation and based on Software hrustworthy Model, we put forward a quantitative as- sessing method named QUEST, which makes use of results of software testing and KDl〕and can attain the objective better.

Key words: Software quality evaluation, Quantitative assessing method, Software trustworthy, Software testing, Knowledge discovery, Software engineering