Abstract: The cruise range of autonomous underwater vehicles(AUVs) mainly depends on the onboard electric power.In order to reduce the power consumption effectively,a small buoyancy changing AUV with the capacity of soft landing and bottom-sitting is developed,which can carry out long time ocean environment measuring missions with the limited power.The general configuration of the AUV is described first.Then the landing strategies of the AUV are discussed in detail.Based on the comparison of three landing strategies,the strategy of diving to the desired position and then landing with controlled water injection is selected.This strategy can confine the impact force in landing process within a safe range,as well as make the landing time shortest.Finally,the landing trajectory is planned.Results of simulations and sea experiments show that the AUV can land safely and smoothly on the sea bottom with the strategy.