What would had happened?if soviet union had shot down apollo 11 rocket down in order to win race to moon?

There'd be an amazing outrage across the world - and of many in the Soviet Union; that flight was covered so well in the press - even within the Soviet Union, people were aware of the mission. Had it been attacked/shot down - it's an outright act of war, and probably would've sparked a missile exchange...

Shooting down another country's space launch, especially a civilian one like Apollo 11, is an act of war. If any one survived the resulting nuclear exchange, going to the Moon would be the last thing on their minds.

How do you think that the USSR could have tried to shoot down the Saturn V ? The US in 1969 had massive naval superiority and so, did have security looking at such defenses while the rocket was on the pad. Inside of two minutes after launch, Apollo 11 was well out of range of any available weapons system the USSR had, even if a Soviet ship could have gotten close enough to try to fire anything.

No one back in 1969 had the ability to shoot down anything in Earth orbit, and Apollo 11 only spent a couple of hours in orbit, before heading for the Moon.

I don't speculate about impossible fantasies.

Yes. declaration of war and all that are all good answers.
However, the Soviets also had a sense of fair play. There would have been WAY too much outrage in the Soviet Union, it might have brought about its collapse.

The real reasons Apollo 11 got ahead of the Soviets (in the race) include the death of the Soviet rocket specialist Sergeii Korolieff (in 1966) AND the idea that they tried to develop a rocket that would serve BOTH for manned trips to the Moon AND to Mars (biting more than you can chew). Korolieff had started the development of the N-1 rocket way back in 1959, already thinking about Mars (and maybe even Venus). He only began to plan trips to the Moon AFTER Kennedy made his announcement.
Until the death of Korolieff, they were somewhat ahead (6 to 8 months, depending who you believe) in the Moon race. After his death, his replacement was unable to finish the work on the N-1.

The Soviets were already WAY ahead in other programs (to Venus, to Mars, etc.); the Moon race was just one of three races for them... and they were winning the other two. They had no need to make it a 3-0 victory, since they already had a 2-1 victory "in the bag".

Even to this day, the only countries trying to shoot down other people's space vehicles are the USA and China.

I'm sorry Elizabeth but you would not be here to ask such a silly question, in fact it is probable that I would not be here to answer it either.

It is pointless surmising about something that did not happen but if the Russians had shot it down (if they were capable of doing so which I doubt, at that time) it would have undoubtedly ended it war and probably nuclear exchanges between both sides and the other nuclear nations.

If this happened it is unlikely anyone would be here anymore.

I think it would have led to an all out war.
The US, and the world, would not have been happy at the shooting down on an unarmed craft

Nuclear war