This study tries to understand key factors in VoIP system from perspective of Taiwanese companies. At the same time, it tries to help VoIP system vendor to make the marketing strategy in the future. Furthermore, it makes some advices to the other studies in the future. Using a physical questionnaire and there are 97 effective responses were obtained. The response rate approximates 69.29%. Using the Principal components analysis, Cronbach α and Independent sample T-test to analyze. The revised model includes five constructs, Perceived Benefits, Organizational Characeristics, Environmenental Characeristics, Decision Unit, and Technology development. Atfer use Descriptive Statistics to understand the key factors in VoIP system from perspective of Taiwanese companies. The ranking list are: (1) Environmenental Characeristics, (2) Perceived Benefits, (3) Technology development, (4) Organizational Characeristics, (5) Decision Unit. The results of analysis indicate, if VoIP vendor can let the customer to know the IT strategy from his most competitive company and provide the better service level. It will be have more chance to implement VoIP PBX in enterprise of Taiwan.