Abstract: The flowback of the fracturing fluid after treatment is significant parts of hydraulic fracturing. The appropriate flowback step may make great contribution to the fracture flow conductivity. This paper focused on the researches of the fracture propagation, fracturing fliud transportation, fracturing fluid loss property, fracture closure and mathematical model of the flowback procedure. According to the theory of petrology and fluid flow in porous media, mechanism of leakoff of fracturing fluid, fracture propagation and 2D dynamic leakoff fracturing fluid of non-Newtonian fluid were established. On the basis of fluid mechanics, lithomechanics and the rule of material balance, mathematical model of fracture closure was established. The mathematical model of proppant settling in power law fluid was set up after analyzing the influential factors on proppant settling. Moreover, the flowback optimization software was compiled. On the basis of predecessors’ and field successful practice’ experiences, these are good for scientific and quantitative design of flowback in fields.