You shouldn't gain weight first and then gain muscle. Thin people gain muscle method: 1. Lay a good foundation, advance a bodybuilding training class, correctly master fitness knowledge and technology, improve their own quality, strengthen the training of muscle strength and endurance, and improve the adaptability of body muscles; 2. Exercise method: exercise large muscle groups, the amount of exercise should be adjusted appropriately, and different instruments can be used to assist; Finally, practice less other sports, which will consume a lot of energy in the process of fitness. 3. Supplement nutrition. First of all, eat more foods containing carbohydrates (such as coarse grains, yam, sugar, milk tablets, etc.). ), can promote the release of insulin in the human body and improve the metabolic level; Followed by protein, which can better promote muscle synthesis.