1. Try https://towelroot.com/ download : https://towelroot.com/tr.apk
2. If towelroot not working, try http://www.kingoapp.com/ supported devices list: http://www.kingoapp.com/android-root/devices.htm
3. If still not working, try search "devices model + root" on Google. such as "LG G3 root".
4. After get ROOT, install SuperSU to manage root: https://play.google.com/store/apps/details?id=eu.chainfire.supersu
More info about Root
We've talked a lot about root and Android in the past five years. We've discussed the good, we've discussed the bad. We'll keep talking about both, because root on Android, like Android itself, is a constantly evolving thing.
As Android matures, the wide-open style of root access we may have grown used to with legacy versions has gone away. Because Android is designed for mobile devices, the focus is on security — specifically the security of your life's data you might have stored away on that screen in your pocket. We've seen Android go from the wild-west days of unfettered Superuser access, to locked down and tamper-proof (well, they try to be) devices meant for folks who need the extra level for their business details. For some of us, this is a hinderance and we don't want Google or the folks who made our phone trying to protect us from ourselves. But for each person who needs — or thinks they need — unfettered root access there are thousands, if not tens of thousands, who just want their data to stay safe. Those people are who our phones get built for, and we're left to exploit as best we can.
Root itself is just a user with elevated permissions, who can do anything to any file or folder in the system. It's often dangerous, always powerful, and an integral part of Linux. Android is the most popular "version" of Linux in the world (as well as the most popular computing system), but as we discussed above superuser access is more restricted than it is on other Linux systems. We don't have to like this, but there is little we can do to change it other than build our own from the AOSP. While I think anyone and everyone interested in building Android themselves should look into it, for now we have to stay in the limits that Security Enhanced kernels and Knox have given us.
If you've read this far, congratulations. Enough talk. It's time to root that device, and we've got the links you need to get started.
Here you'll find links to tutorials for the devices that are hot right now. Don't worry if yours isn't here, we've got a big list of archives further down the page.
Here you'll find the tried and true Android favorites that are still current and popular, but not the newest models. If you're shopping for a phone just to root, these are the models you'll want to look at, while developers and hackers work on the latest hot devices to open their secrets.
Androids that work too well to just ignore. Some of our favorite devices are in this section, and rooting helps give them life a little longer than the manufacturer provides.
If your device isn't listed here, we suggest you visit the Android Central forums and ask some of the root-savvy users you'll find there. This is your best bet at finding root for devices that are no longer as popular, but still very serviceable.