My son is 13 year old and his body weight is 105kg with a height of 166cm. what kind of exercise will help him to reduce his weight?

Reduce calories.: To lose weight, one needs to take in less calories than the body uses, or it is stored as fat. The best way to achieve this is to do a combination of eating less and moving more. With any exercise plan, esp for a teen, it is best to pick something that is enjoyable, inexpensive, social and readily available or it will feel like punishment.