A cellular automata (CA) model for the spread knowledge between knowledgebased organization and its members was established.  The influencing factors and the rules of tacit knowledge spread among knowledge-based members were stimulated. The results indicate that (1) the trusts among members in the knowledgebased organization, the wills and influence force of the knowledge disseminators and the status of the initial knowledge disseminator are correlated positively with the speed of spread knowledge; (2) flat organizations benefit to down to up-spread knowledge and (3) instantaneous speeds of spread knowledge in the organizations will reach the most value when the knowledge levels of the organization reache their optimal scales of the spread.