In order to study the sealing characteristics of DAS composition seal ring of automobile crane leg cylinder,a ring sealing characteristics analysis model was established by ABAQUS to analyze the impact on the VonMises stress,contact stress and contact length caused by the initial compression and oil pressure.The results show that VonMises stress,contact stress and contact length are increased along with the increasing of initial compression and oil pressure.The contact stress of main lip presents a quadratic distribution along the contact length when the compression is less than 0.4 mm under the initial assembly state,and a bimodal Gaussian distribution when the compression is greater than 0.4 mm.In the static sealing state,the contact stress of main lip is bimodal Gaussian distribution when the initial compression is 0.5 mm.The contact stress of the main lip,vice lip ,and the bottom is always greater than the oil pressure,meeting the sealing conditions.