I have bought a DJI phantom 3,  and I have used it about 6 months. Now I found my lipo battery can only support my drone fly too short time. I know every lipo battery has its use life, I think my battery's capacity get small, so the only way is change a new lipo battery. My lipo battery is 15.2V 4480mah, so I have a question: if I can find a lipo battery which is the same to its official lipo battery, can I use it to replace the official battery ?

As long as the delivered voltage and physical size suits the phantom, you should be good. Although i bet the DJI-reps will advice you not to do this for several reasons. My advice, stick to the original batteries as they are made for the specific model you possess, and of course all warranty will be long gone if something were to happen.

It's recommended to buy DJI official Intelligent Battery from authorized dealer, since we could not guarantee the performance with other batteries even through voltage and physical size suits the aircraft.