The original structure of the cutterhead needs to be improved; and the mechanical properties of the cutterhead need to be analyzed before and after modification so as to realize shield tunneling in medium sand stratum with rich water. The theoretical calculation of the cutterhead load under conditions of earth pressure balance and unbalance is implemented; and then the finite element method is used to study the stress and deformation of shield cutterhead before and after modification. The study results show that: 1）The maximum equivalent stress and the maximum deformation of the cutterhead under condition of earth pressure unbalance are higher than that under condition of earth pressure balance. 2）For the same condition, the maximum equivalent stress of cutterhead varies little before and after modification; while the maximum deformation increased by about 10%; the maximum equivalent stress is located in the cutter plate and the bracket; and the maximum deformation is located in the bottomleft edge and the aboveright edge of the cutterhead. After modification, the strength and rigidity of the cutterhead can meet the construction requirements; and it has good tunneling effect and efficiency.