My height is 6.4 feet can i reduce my height about 3 to 4 inchs so that i look normal i am18 year old, and i want to stop growing now .help me?

Don't Stop Growing!: Your growth trajectory is linked to your genetic history (meaning; "are your parent's tall"?). See your doctor to asses whether there is a pituitary disorder that is potentially triggering this growth spurt. Trying to induce growth or stop it is sometimes clinically warranted but the vast majority of times it's just mother nature and it's best not to mess! please get checked out!

Tough to stop: Your growth plates are still open, so some degree of growth will continue. The only way to reduce your height is to have bone removed from your legs. This is generally considered to be "not a good idea." 6' 4" is not considered a giant by today's standards.

You're fine: Get comfortable with whatever height Mother Nature gave you. If you try to change your looks, the people who like you for who you are will say, "Hey! You should look like YOU!" Most guys who are a little taller than most like it -- one of my best friends is 6'8" and loves it. It's probably a social plus. Talk with some folks about your being tall and I think you'll end up happier with it.