There may be many reasons why a kitten has a big belly. Here are some common possibilities:

Eating too much: The kitten may have eaten too much food, causing its belly to look larger. Make sure to give the right amount of food and avoid overfeeding.

Hairball accumulation: Kittens may have swallowed too much hair, causing hairballs to accumulate in the intestines. Kittens can be given products to help digest hairballs, such as cat grass or a specialized hairball lubricant.

Parasitic infection: An internal parasitic infection may cause the tummy to swell. Regular deworming is important.

Digestive problems: Indigestion, intestinal inflammation, or other digestive problems may cause bloating. Watch your kitten for other unusual symptoms, such as vomiting, diarrhea, or loss of appetite.

Disease or organ problems: Certain diseases or organ problems can cause abdominal swelling. If you are concerned, it is best to take your kitten to the veterinarian for a check-up.