Laptop No power

There's a short in the system somewhere.  Several possibilities:

1.  The DC jack in the system is faulty.  On most newer system, that's the place to start - but we'll need to know exactly which system you have to determine whether the jack is replaceable.  That is, Inspiron N5110, 5531, etc.

2.  One of the USB ports has shorted pins (check inside the USB ports with a flashlight for pins making contact with both sides of the port.  If one or more of the ports is faulty, it may be a matter of replacing a small board -- or it may require a mainboard replacement.

3.  If neither of those is the cause, it's the mainboard that's bad.  On low-end models, or systems over 3 years old, it's really not worth replacing the board - the system should be replaced.

Thanks for the response.
I have Dell Inspiron 3542 core i5 and I bought 2 years ago
And can you tell me if any of your suggestions needs inspection. Will I lose my data of laptop. I have so much documents there even on desktop too. So by changing the motherboard or any other things, is there a risk of loosing data ?

Probably not, but there is ALWAYS the possibility of a sudden hard drive failure, so keeping backups is essential either way.

If you're not sure where to start, replace the DC jack first:

www.parts-people.com/index.php

If that doesn't solve the problem, look at the USB ports next -- though it looks like if those are faulty, it means a mainboard replacement.