The reasons for a lot of water under the car floor mats are: 1. The sunroof is not tightly sealed, and the water leaks from the sunroof to the under the car floor mats; 2. The water flushed into the car was not cleaned up when washing the car; 3. The warm air in the car is corroded. Cause water to leak under the car mat; 4. The car weather strip is aging. The solution to a lot of water under the car mat is: 1. Take out the car mat to clean the remaining water in the car; 2. Open the car door to dry; 3. Adjust the vehicle cycle switch to the internal circulation to drain the steam through the air conditioning system ; 4. Replace the car floor mats with those with waterproof performance; 5. Check whether the drainage pipes of the sunroof are blocked.