As stated in the other answer, it is indeed illegal. I would then address the second question, "to watch porn videos it will be cause your arrest in UAE ?" There is difference as enforcement of certain illegal activities in UAE doesn't seem to happen. For example sex outside marriage is illegal in UAE, but lots of visitors practice it without consequences. A quick google search didn't find any single case of someone actually being arrested for watching porn in UAE, so the enforcement seem to be equally weak.
Practically, watching them in privacy, such as your hotel room, despite being illegal, should be safe. Unless your room is wired for video recording, it would be a challenge to prove that (a) you (b) watched porn. And there is no obvious incentive to do so.
However watching them in a public place, or using your employer's Internet access for this (if you work in UAE) can indeed lead to arrest.