Abstract: Based on a 2D numerical simulation method, the stiffness effect of reinforcement mass in bottom of deep excavations was studied. It is found that, with the enlargement of stiffness of reinforcement mass, the settlement of ground, the heave of bottom and the horizontal displacement of supporting pile decrease, the positive and negative bending moment tend to be symmetry and the absolute values do not increase the stability safety factor of whole deep excavation due to the increase of the stiffness of reinforcement mass; when the half of bottom width of deep excavation is reinforced, the heave of bottom of another half is influenced slightly by the increase of reinforcement mass, the heave curves of bottom belong to step shape, and the heave value in non-reinforcement region is far larger than that in reinforcement region. Six correlativity curves (that is the maximum of ground settlement, the maximum of heave value of bottom versus reinforcement mass stiffness) established in this paper show that the settlement of ground and the heave of bottom tend to be uniformity when the stiffness of reinforcement mass reaches a certain extent. This indicates that the increase of the stiffness of reinforcement mass in bottom is favorable to a deep excavation. Six correlativity curves have definite reference value for other deep excavation engineering.