To get the straight flight features of agricultural UAV(unmanned aerial vehicle)，and to verify and evaluate the artificial path planning and the actual operating results in visual remote flight mode, a wireless transmission system based on GPS was designed. The handler took the straight boundary of paddy field as a reference by using remote control UAV based on visual and experience. Straight flight experiment and the real time path planning flight experiment were implemented on the base of the paddy field boundary. The results showed that it was difficult to control the UAV flying in a straight line in visual remote control mode, and the artificial planning route deviated from the ideal flight path significantly for the reason of no reference. It was estimated that the skip rate was 17.1%, duplication operation occupied 8.2%, and outside wasted region accounted for 0.7%. Meanwhile, the height and speed of the UAV had a characteristic of erratic randomness in visual remote flight mode. Therefore, in case of no navigation, it is difficult for handler to implement precise operation by means of visual and experience alone. Autonomous flight mode with GPS navigation, intelligent optimization and generates flight trajectory, is the direction for future development of UAV applied in precision farming.