Through wave section physical model experiment,the stability of the mattress of seawall with hinged concrete slab mattress revetment is studied under different conditions such as water depth,wave height,wave period,wave type and ballast block’s space.The characteristics of instability for different parts of mattress are revealed.The experiment results show that the stability of mattress is worse under the circumstance that wave height is higher or wave period is longer when the water depth is the same.The impact action of irregular wave on the stability of mattress is significantly more than action of regular wave.The instability of mattress occurs mainly in the edge of head and tail part,and the stability of internal part is better.The mattress still has good stability when it uses the structural type that the edge of head and tail ballast block with large thickness and the internal ballast block with small thickness.Ballast block’s space should be determined rationally with consideration of all factors in actual engineering because it will influence the stability and the ability of abrasion-resistance,deformation and beach protection of mattress and the selection of gravel cushion.