Rock 3a could not boot into Android

I have bought a rock3a board, and download the android img from radxa website, after I flash the img into sd card, and boot up from sd card, the system could not boot succesfully: After power on, the screen would show “Rockchip Kernel”, after that, the screen would show “error”, and then reboot.

I have flashed ubuntu img into sd card, the Ubuntu could boot up successfully.