The Qiangtang basin is the largest Mesozoic marine sedimentary basin in China. However, a comprehensive understanding of the basement properties and deep structural characteristics of the basin is not yet available. The latest high- precision airborne gravity and magnetic data were used to constrain the basement properties and deep tectonic patterns of the Qiangtang basin. The gravity and magnetic field maps show that in contrast to the Southern Qiangtang block, the Northern Qiangtang block displays “high magnetic and low gravity field”. Also, the magneticity of the basement in the Northern Qiangtang is significantly stronger than that of the Southern Qiangtang. In addition, the calculation results show that the basement of Northern Qiangtang depression is deeper, generally between 7. 0~15. 0 km, and there are 6 depression centers. The basement of the Southern Qiangtang depression is slightly shallower, mostly in 5. 0~13. 0 km, with 3 depression centers. The obviously differences in gravity and magnetic field indicate that there is no unified Precambrian basement in this basin, and the Northern and Southern Qiangtang blocks may be composed of completely different tectonic units. The consecutive central uplift belt divides the Qiangtang basin into two parts, presenting a structural pattern of “two depressions sandwiching one uplift”. In this study, 31 raised area and 9 sag areas were identified in the Qiangtang basin.