On your Android phone, go to Contacts app. Tap Contacts tab.
The following steps are a little different according to your mobile phone. Here I list out 2 situations. Hope it's useful.
Situation 1. (Android 4.04)
Tap the virtual button left to the home button to show the menu. Choose Import/Export > Export to USB storage or Export to SD card. Then, contacts will be exported as a vCard file and saved on SD card of your Android phone.
Situation 2. (Android 4.4.2)
Tap Contacts app > Contacts tab. Go to the upper right corner and click the button next to a cross-like button. In the drop-down menu, choose Settings > Contacts > Import/Export > Export to USB storage. Then, contacts will be saved as a vCard file on the SD card of your Android phone.