Diurnal evaporative testing of atmospheric fuel system with no-load canister for 14 days and half load canister for 7 days is carried out according to the US EPA BETP test procedure. In addition, the atmospheric fuel system and pressurized fuel system were tested for BETP for 72h diurnal evapration respectively.The results show that the total emissions of the atmospheric fuel system in 72h is 210mg, and the proportion of respiratory emissions is between 90% - 95%. The 72h total emissions of the pressurized fuel system is about 120mg, and the permeation emissions of the fuel tank accounts for about 82% - 90%. The total respiratory emissions of the atmospheric fuel system are 130.4 mg, mainly alkanes, accounting for 70% - 80%. The pressurized fuel system is dominated by the permeation emission of the fuel tank, with a total amount of 127.5 mg, mainly composed of alkanes, aromatic hydrocarbons and OVOCs, accounting for 45% - 50%, 43% - 47% and 3% - 5% respectively. In the canister breakdown test of gasoline vehicle fuel system, the THC emissions of no-load test and 7-day half load test are similar; the VOCs composition in the first 12 days is similar to that in the 3-day test, mainly alkanes. After the canister breakthrough, the proportion of aromatic hydrocarbons and OVOCs increases significantly.