Subsurface flow constructed wetland system capable of switching between series connection and parallel connection

The utility model provides a subsurface flow constructed wetland system capable of switching between series connection and parallel connection, which comprises a plurality of subsurface flow wetland units, and each subsurface flow wetland unit is provided with an independent water inlet system and an independent water outlet system; a controllable water inlet valve and a controllable water outletvalve are respectively arranged on the water inlet system and the water outlet system; connecting pipes are arranged between the subsurface flow wetland units with the upstream and downstream relationand between the water outlet system of the previous-stage subsurface flow wetland unit and the water inlet system of the next-stage subsurface flow wetland unit, and controllable communicating valvesare arranged on the connecting pipes. The water head of the water inlet system is higher than the water head of the connecting pipe which is higher than the water head of the water outlet system. Through adjustment of the cont