Multiplexin 5V?

I want to multiplex my arduino uno's 5V connection. Can it give damage to my arduino?

More details please

What exactly do you want to do ?
Have you got a schematic ?

If by multiplexing 5v you want to power other devices with it? You have to be cautious about the amount of current you pull. The Arduino has a small linear regulator that has limited current. Depending on which one is on your board it’s good for about 100 mA. Keep in mind if you’re powering through Vin at 12v you’re dissipating the difference as heat, use Ohms law and power conversion calculation. The onboard power supply is mainly just to power the Arduino and a few low powered items like LEDs. If you’re doing this do the calculations and check for overheating.