This research aims to predict the sale amount of 3G mobile phone market of Chunghwa Telecom by GM (1, 1) four items model and regression of 3G developing trend and attempts to formulate the suitable countermeasures for 3G development. The result of this research is that the grey prediction theory can fit the four-term development precisely in the 3G market. The accuracy of the prediction result is above 90% and corresponds with a distinction, which the grey theory can meet expectations with small samples or data. In addition,the accuracy of GM (1, 1) four items model is higher than that of the regression model﹒For example, along with the 1.8 million users from December in 2005 to September in 2007, the results not only show that Chunghwa Telecom will reach the line of 7.5 million users in 2009, but also indicate that 3G market will become mature in a long run and keep growing up in the near future. As such, the importance of 3G mobile market is foreseeable; therefore, the operators ought to make a great effort to allocate the marketing resources as early as possible. The suggestion of this research is that under the circumstances of fierce competition, Chunghwa Telecom as a leader can cooperate with the other operators to further the interests of the 3G market and in turn paves a way to the future 4G market.