It's not illegal, but it depends on whether the wallet belongs to the lost property or forgetting things. If it belongs to forgetting things, the person found should be returned. The first paragraph of Article 270 of the Criminal Law of People's Republic of China (PRC) stipulates: "Whoever illegally occupies other people's property and refuses to return it shall be sentenced to fixed-term imprisonment of not more than two years, criminal detention or a fine; If the amount is huge or there are other serious circumstances, he shall be sentenced to fixed-term imprisonment of not less than two years but not more than five years and fined. " The second paragraph stipulates: "Whoever illegally takes forgetting things and buried objects of others as his own, and refuses to hand them over in a large amount, shall be punished in accordance with the provisions of the preceding paragraph."
According to the above-mentioned provisions of Article 270 of the Criminal Law of People's Republic of China (PRC), only if the actor illegally takes another person's forgetting things for himself and refuses to hand it over in a large amount, it constitutes the crime of embezzlement. Forgetting things doesn't mean losing property. Lost property refers to the property lost by the owner. It takes a relatively long time to lose control of property, and the specific time and place are generally unknown. Scavengers generally don't know, and it's hard to find lost people. The forgotten thing is only temporarily forgotten, and the forger lost control of it in a relatively short time. Generally, they will quickly recall the forgotten time and place and come back to look for it, while scavengers generally know who the forgetters are.