With the tightening of emission regulations, Electrically Heated Catalyst (EHC) are an important technical solution for diesel vehicles to address the emission challenges of cold start and Real Driving Emission (RDE). This paper investigates the impact of EHC coupled exhaust aftertreatment system (Diesel Oxidation Catalyst (DOC) + Selective Catalytic Reduction Integrated into Diesel Particulate Filter (SDPF) + Selective Catalytic Reduction (SCR) - Ammonia Slip Catalyst (ASC)) on the energy consumption and emission characteristics of light-duty diesel vehicles based on the World Light Vehicle Test Cycle (WLTC) and RDE. The research results show that under WLTC conditions, compared to EHC off, the time for the SDPF inlet temperature to reach 180 °C when EHC on is 44 seconds earlier. The Carbon Monoxide (CO) emission of diesel vehicles is 63.5 mg/km, the Total Hydrocarbon (THC) emission value is 44.9 mg/km, the Non-Methane Hydrocarbon (NMHC) emission value is 39.5 mg/km, and the Nitrogen Oxide (NOx) emission value is 27.4 mg/km, which is far below the limit requirements of CHINA VI b and Euro 7. Among them, the average urea injection rate increased by 1.1 mg/s, and the overall NOx conversion efficiency increased by 7.1% compared to the EHC off, reaching over 94%. Fuel consumption increased by 1.64%. Under RDE conditions, compared to EHC off, the NOx emission during the urban operating phase when EHC on have decreased from 129.7 mg/km to 7.9 mg/km, the NOx conversion efficiency increased by 34.8%. The NOx emission throughout RDE have also decreased from 51.5 mg/km to 6 mg/km, the NOx conversion efficiency increased by 13.8%. This is an important technical solution to meet the requirements of the next phase of the CHINA VII emission regulations.