In order to slow down the rising velocity of water content in production liquid during unconsolidated sandstone reservoirs development and improve the effect of tip screen out fracturing sand control，octadecyltrichlorosilane（OTS）was used to the treatment of hydrophobic modification on the surface of propping agent（quartz sand）by self-assembly method. The effect of OTS solution concentration，soaking time and air drying time on the broken rate，acid solubility and fluid resistance ratio（NFRR value） of OTS self-assembled hydrophobic quartz sand was studied. The condition of modification treatment on the surface of quartz sand was optimized by orthogonal test，the flushing resistance was determined，and the self-assembled monolayer formation mechanism and the hydrophobic mechanism were introduced. The results showed that the OTS solution concentration had the greatest influence on the broken rate while the soaking time had the greatest influence on the acid solubility and NFRR value. The NFRR value of quartz sand after soaked one hour by 10 mmol/L OTS solution and air dried 84 hrs got peak point 2.531 with the best hydrophobic result. OTS self-assembled hydrophobic quartz sand had an excellent hydrophobic performance and the water permeability of core could keep stable after 5 days scoured by deionized water. OTS self-assembled hydrophobic quartz sand had a stable surface property and it could satisfy the need of tip screen out fracturing sand control.