In view of the problems with the existing cuttings flow measurement system， such as incomplete cuttings dumping in the actual working process， the risk of borehole cleanness， wellbore stability， for which the specific evaluation method has not been formed， this paper analyzes the factors affecting horizontal well borehole cleanness， and puts forward the technical scheme for cuttings flow measurement based on cuttings sweeping， solving the problem of incomplete dumping of rock cuttings in the previous process of rock cuttings flow measurement with reduction of the manual cleaning frequency. Based on the return rate of rock cuttings， the quantitative monitoring method of wellbore cleanness and wellbore stability has been established， and the risk monitoring and evaluation method of wellbore cleanness and wellbore stability formed. Through the field application test， the risk of wellbore uncleanness and wellbore instability has been successfully warned， which proves that the method established in this paper can be applied to the field construction.