The invention discloses a water-electricity connecting structure of a large-small coil parallel circuit of a dual internal water cooled generator rotor. The connecting structure comprises a group of coils located at the innermost end and at least one group of coils surrounding outside the first coils. The connecting structure is characterized in that large and small coils of each group of coils are connected in parallel, exciter-end bottom wires of the large and small coils of the first coils are jointly connected with a bottom wire water inflow corner, exciter-end bottom wires of the large and small coils of each of the other groups of coils except for the first coils are connected with a bottom wire water inflow corner every other group of coils, turbine-end surface wires of the large and small coils of each group of coils are connected with a surface wire water outflow corner every other group of coils, and water ways of the large coils and water ways of the small coils are not crossed. A feasible water-electricity connection method is provided for the dual internal water cooled generator rotor under the condition that the large-small parallel coil of the rotor is adopted, cooling of the rotor coils is guaranteed, and normal operation of a unit is ensured.