A safe syringe, comprising: a barrel having a barrel body , an accommodating chamber , a seat mounting hole and a seat clamping slot ; a needle seat having a seat body mounted in the seat mounting hole of the barrel , and a needle hole ; a hook rod , a linkage deformation portion connected to the hook rod , and a barrel clamping portion connected to the linkage deformation portion , linked thereby and capable of being clamped into the seat clamping slot of the barrel ; and a plunger having a rod body , and a hook insertion hole which is capable of being sleeved with the hook rod of the needle seat and compressing the linkage deformation portion for elastic deformation such that the barrel clamping portion of the needle seat is not clamped into the seat clamping slot of the barrel , the hook insertion hole being capable of hooking the hook rod of the needle seat to move the needle seat such that the needle seat is tilted to one side due to the cooperation relation between the linkage deformation portion of the needle seat and the hook insertion hole of the plunger wherein the hook rod extends from the seat body , the linkage deformation portion is in the shape of a convex arc-shaped sheet that is located at one longitudinal side of the needle seat such as to provide the linkage deformation portion with deformation space, one end of the linkage deformation portion being connected to one end of the barrel clamping portion and the other end of the barrel clamping portion being connected to the seat body and the other end of the linkage deformation portion being connected to the hook rod , and the convexity of the linkage deformation portion being oriented away from the hook rod , and a vertical distance (L1) from a centerline of the needle seat to an outer edge of the hook rod is smaller than a vertical distance (L2) from the centerline of the needle seat to an outer edge of the linkage deformation portion . a barrel having a barrel body , an accommodating chamber , a seat mounting hole and a seat clamping slot ; a needle seat having a seat body mounted in the seat mounting hole of the barrel , and a needle hole ; a hook rod , a linkage deformation portion connected to the hook rod , and a barrel clamping portion connected to the linkage deformation portion , linked thereby and capable of being clamped into the seat clamping slot of the barrel ; and a plunger having a rod body , and a hook insertion hole which is capable of being sleeved with the hook rod of the needle seat and compressing the linkage deformation portion for elastic deformation such that the barrel clamping portion of the needle seat is not clamped into the seat clamping slot of the barrel , the hook insertion hole being capable of hooking the hook rod of the needle seat to move the needle seat such that the needle seat is tilted to one side due to the cooperation relation between the linkage deformation portion of the needle seat and the hook insertion hole of the plunger wherein the hook rod extends from the seat body , the linkage deformation portion is in the shape of a convex arc-shaped sheet that is located at one longitudinal side of the needle seat such as to provide the linkage deformation portion with deformation space, one end of the linkage deformation portion being connected to one end of the barrel clamping portion and the other end of the barrel clamping portion being connected to the seat body and the other end of the linkage deformation portion being connected to the hook rod , and the convexity of the linkage deformation portion being oriented away from the hook rod , and a vertical distance (L1) from a centerline of the needle seat to an outer edge of the hook rod is smaller than a vertical distance (L2) from the centerline of the needle seat to an outer edge of the linkage deformation portion . <EOS>