Hi,
When i am switching relay on and off i am seeing some fluctuations in my DC supply, I am using freewheeling diode also. I am not able to solve this problem. Please advice some solution for this problem.

 

Please Post your circuit along with power supply and relay datasheet means power supply capabilities

 

if the supply provides power to to the switched contacts of the relay ← (then) it's trivial

if the supply does not provide power to to the switched contacts of the relay ← it's the relay coil being connected(/powered) and disconnected(/un-powered)