Jose Canseco -- Threatens Daughter's BF ... Treat Her Right or I'll Shoot You

Jose Canseco says he has a game plan for the first time he meets his daughter's famous BF Mike Stud -- "I'm gonna answer the door with a gun in my hand and see how he reacts."

(He's clearly joking).

Jose was out in in L.A. this weekend when we asked how he felt about his model daughter Josie Canseco dating the rap star. Jose says he likes the guy -- but he's not taking any chances.

"All I know he better treat my little girl right ... 'cause if he doesn't he's gotta deal with me, all 6'4", 260 pounds of me ... and that's gonna be ugly Mike Stud."

FYI -- Mike says he's head over heels for Josie and even featured her in a music video for the song he wrote about her. She's in a thong.

Wonder how Jose feels about that?