My son is 6 years old he is vomiting since last night none of the vomiting medicine is staying in what must i do take him to the hospital ?

Depends: At that age many can stay hydrated by sucking on ice chips or sipping re-hydration fluids in small quantities. If he tolerates small amounts frequently you can increase the amount over time. If he can make pee at least every 6-8 hrs he is hydrated enough to be managed at home. If he doesn't pee after 12 hrs he is getting dry & may need hospital care.