Air outlet cover, design method of air outlet cover, fan system and range hood

The invention relates to an air outlet cover, a design method of the air outlet cover, a fan system and a range hood, the air outlet cover comprises a hollow cover body, an air inlet and an air outlet, the air inlet and the air outlet are formed in the two ends of the cover body respectively, the end face, where the air inlet is located, of the cover body is recorded as a first end face, and the end face, where the air outlet is located, of the cover body is recorded as a second end face; the second end face gradually inclines towards the first end face from top to bottom. The exhaust hood is characterized in that the second end face gradually inclines towards the first end face from top to bottom, so that under the condition that the aperture of an air outlet of the exhaust hood is not changed, the structure of the exhaust hood can be effectively prevented from exceeding the exhaust hood, a decorative hood of the exhaust hood is easy to shield the exhaust hood, and the attractiveness of the exhaust hood is i