I haven't gain weight but my face much bigger than before, i had enough water and don't eat high sodium food, what is the reason?how to make it small?

Fat or water: If you have recently gained weight, your face will be bigger from fat. If you haven't, then you may have swelling from fluid, which can have many causes. Best to see a doctor for an initial check to make sure there isn't a medical reason for facial swelling. (rarely, this is the result of kidney problems, low protein level, excess corticosteroids, vein blockage, etc.) good luck.