Hello there, Phyu Win Thant.
It sounds, from what you're describing, that your MacBook Air is no longer powering on. The following Knowledge Base article offers up some great steps for troubleshooting:
If your Mac won't turn on - Apple Support
First, rule out the display as the source of the issue. To be sure you're not having a display issue, press your computer's power button. If your computer has power but doesn't have any video:
- You may hear a startup chime.
- You may hear fan or drive noise.
- You may see a light from the Sleep LED (if your Mac has one).
- Pressing the Caps Lock key on the keyboard causes it to light.
If any of these things happen, see Troubleshooting: My computer has no video. Otherwise, continue with this article.
After ruling out display issues, and if your computer won't turn on, try each of these steps.
- Verify you have a good connection from your Mac to the wall outlet by confirming the power cord and adapter are securely connected and plugged in. To check if the wall outlet is working, plug in a lamp or other electrical device
- If the wall outlet is working and you continue to have no power, try another power cord or adapter if available. If it works you may need a replacement cord or adapter. If you're using a Mac notebook, see Apple Portables: Troubleshooting MagSafe adapters for further troubleshooting with MagSafe adapters.
- Disconnect all accessories that are plugged in to your computer. This includes things like printers, USB hubs, or mobile devices.
- Hold down the power button for ten seconds. Then, press the power button again to see if the computer turns on.
- Reset the SMC.
- If you recently installed memory or a drive in your Mac, make sure it's compatible, supported, and installed correctly. If possible, reinstall the original memory or drive to see if the issue persists afterwards.
- If you're still unable to start up your computer after trying each of these steps, visit an Apple Store or Apple Authorized Service Provider (AASP) for further diagnosis. If you plan to visit an Apple Retail Store, make a reservation at the Genius Bar using http://www.apple.com/retail/geniusbar/ (available in some countries only).
Thanks for being a part of Apple Support Communities.
Kind Regards.
