Unmanned aerial vehicle (UAV) “precision agriculture” task requires UAVs to respond to environmental information and make decisions autonomously, so as to complete the task of spraying. Firstly, the design rules of space attributes are studied which meet the task requirements, according to the range distribution characteristic and the sample density of the accurate operating condition attribute factor, a discretization method of precise quantization is proposed which is based on arctangent attribute and Gaussian distribution density. Then, the attribute reduction based on the attribute dependence of the rough set is solved and used to remove redundant attributes, and the rough decision rules table is obtained for precise operation. The rationality and accuracy of the rough decisionmaking method is verified by the experiment.