my amplifier s power cable is not long enough to reach battery . so is there any problem if i take another piece of power cable and then attach them ?
It's safe enough, as long as you make a good splice, and insulate it well. For automotive use, I like insulated, crimp-on splices. If this is a really high-power setup, and the power cable run is that long, you may be better off replacing it with heavier-gauge wire.
Solder and insulate your splice. That's the only concern.
