@vignesh said:

I build al the img files required . flashed system.img, boot.img and recovery.img (build twrp recovery) over fastboot. now the mobile stuck at ASUS logo while turn it on.. please help

You must not use inline kernel building because this way you will get a broken kernel.
You should figure out which ramdisk is needed for Ubuntu Touch. And make changes in stock ramdisk for this.

@vignesh said:

@tank0412 please see what's wrong with my kernel link download now
i already extract this img file but i have n idea about the ramdisk inside this file
Thanks

As i said earlier you got a dead boot.img due to inline kernel building.
So you should do all stuff manually.
And read this:
https://developer.ubuntu.com/en/start/ubuntu-for-devices/porting-new-device/
Device-specific changes
Adapt the Ubuntu kernel: building for an Android device

@vignesh said:

I build al the img files required . flashed system.img, boot.img and recovery.img (build twrp recovery) over fastboot. now the mobile stuck at ASUS logo while turn it on.. please help

You must not use inline kernel building because this way you will get a broken kernel.
You should figure out which ramdisk is needed for Ubuntu Touch. And make changes in stock ramdisk for this.