For the drilling construction in broken formation, it is important to improve the cementation of fractured rocks, rapidly seal the formation fracture to form whole borehole wall and use proper flush fluid for borehole wall stability. With anti-sloughing lost circulation agent while drilling and modified asphalt, the effective formation fracture sealing and higher borehole wall bearing strength can be obtained. The LBM and grafted starch flush fluid systems have good wall building property and rheological property with good application effect for the construction in broken formation.