Gansu province is a developing region. The strength of industrial economy is weak and the level of urbanization is low. It leads to little accumulation of economic energy. Therefore, the whole radiation of cities is weak in Gansu. The chief forms of economic radiation are dot-radiation and line-radiation. That is to say, the economic energy of Gansu is chiefly at the range of dot-radiation and line-radiation. It is an effective and in evitable development strategy to develop the region economy at the range of dot-radiation and line-radiation in the lead,and finally promote the economic development of its surrounding region by its increasing economic radiation. In this paper, take the model of breaking point as the way of quantitative analysis. We use the geometric mean of non-agricultural population and value added of non-agricultural industry in the urban district to measure the cities' scale, and calculate the position of breaking points and the radiation power at breaking points basing on the cities' scale and the distance between two cities by the breaking point formula. Furthermore, choose the radiation power with the strong actual economic significance as the boundary radiation power, and take the boundary radiation power as the basis to calculate the economic radiation radius of 14 main cities of Gansu province by the radiation radius formula. According to this quantitative radiation range, analyze the feature of dot-radiation and line-radiation in Gansu, and give advice for the delimitation of economic cooperation area, the urbanization strategy and non-balanced development strategy.