The paper discusses mainly the necessity that new concepts on costs Fc in fau1ty circuit and measures T of faulty testability are introduced in the four va1ues dynamic costs ana1ysis method，based on the literature [10]. And comparing the four Values analysis with the two va1ues analysis of literature [1] comes from the following three aspects: faulties that can't be detected are predicted，efficiency se1ecting patterns of faulty sensitization and assigning line Values，we come to the conclu sion that testability measures defined in the four va1ues ana1ysis are rea1isticer than the two va1ues in an aspects near real digita1 circuits and better in an effects for speeding test generation. In practice has been indicated that when the four va1ues analysis is applied to automatic test generation system ATGS，computer CPU time economized equals three times of the two va1ues.