If you mean the Magic Kingdom, no, you cannot walk to the park. You take a tram from your car to the Ticket and Transportation Center. You can then decide if you want to ride a boat or the monorail. This will take you to the entrance of the MK.
If you are at another park, you could walk to the park from your car, which is faster than the tram if you are close. If you are parked further away, the tram is your best bet to saving yourself some extra walking.