Research conclusions：(1)The track stiffness increases with the increasement of the ballast depth，but the increasement Is small．The ballast depth has little influence on the track elasticity．(2)With the increase of the ballast depth，the stress on the subgrade surface is reducing，when the ballast depth reaches 350 mm，the stress on the subgrade surface is 0．12 MPa，the safety coefficient has already been up to 1．5．(3)With the increase of the ballast depth，the acceleration of ballast is reducing，SO it is the same with the rate of residual track deformation．With other conditions no changing， When the ballast depth rises from 250 mm to 350 mm，the rate of residual track deformation reduces by 66．12％，which will reduce the maintaineance work greatly，and prolong the service life of track bed．(4)It is suggested that the ballast depth adopts 350 mm in the Tinaco—Anaco Railway line．(5)The research method and conclusion can be applied to similar projects．