In this paper, we introduce the combination of   thermostat control strategy (TCS) and DC-link voltage control strategy to improve fuel economy for series hybrid electric vehicles (HEVs). The main method is tuning essential parameters, including a parameter under DC-link voltage control and a selected constant as an important judgement condition of charging operation modes under TCS. The minimum mass points of equivalent fuel consumption (EFC) corresponding to a series of variables are marked for worldwide harmonized light vehicles test procedure (WLTP). By analysis and verification, the fuel economy of series HEVs with WLTP performs better with the combination control schemes than individual control scheme, so this scheme proves very effective for series HEVs driving in an urban environment.