Taking the specific design of construction and geological conditions of An-ping tunnel in Long-tang to Lang-tang highways in Hunan Province as the background, the construction process of An-ping Tunnel excavated by CD method is simulated by using finite element software Abaqus CAE 2016. Comparing the influence of different size karst caves on the stress and displacement of surrounding rock around the tunnel vault and arch side, the variation diagram of the stress field and displacement field of surrounding rock caused by karst caves of different sizes is drawn, and the variation law of surrounding rock caused by karst caves in tunnel in karst area is analyzed. The results show that the increase of the size of the existing top concealed karst cave in a certain range will lead to the increase of the tunnel displacement and the increase of the tensile stress of the surrounding rock. The results can provide technical support for the construction of tunnels in karst areas.