Depends on what this guy is to you. If he's your boyfriend, then you definitely have to tell him...maybe not right on the face, but more subtly, using an excuse if neccessary.
If he's a friend, tell him not to, with an excuse if need be ( depending on the closeness) but make it more firm.
If he's just an acquaintance, tell him point blank to stop bothering you.
Chat with our AI personalities
Ask him to text you less.
but that might make him a little sad so you can tell him that you love him but you're sometimes busy and you can't spend all your time texting him