Based on the overall analysis of the floating population among big and medium-sized cities in China, thispaper, by means of statistics and questionnaires, makes a systematical study on the migratory features of the floating population in Mianyang, its employment structure, migrating causes and channels. According to the findings, the author finds a fact that with the strategy of Western Development, and with the construction of science and technology city of Mianyang, the migrating in Mianyang conforms to the general patterns of the migration, which has happened in those big and medium-sized cities in China. In addition, the city has a new but unique feature - economic factor, as the driving force of population migration, is quite distinct from that of those cities in eastern areas of China.