Abstract: The fields of detecting,controlling and machine designing should be studied to improve the automatic control level of planting machines.This paper introduced a tentative discussion on the method of automatic detecting,and presented a way of using ultrasonic technology to choose the planting point of the area.The feasibility of the detecting part was analyzed on the basis of ultrasound detecting theory,and then a detecting system for simulative experiment was built.The conclusion from the test and data analysis shows that it is feasible to use ultrasonic technology in detecting obstacles in the planting areas.