The Belle PID system consists of TOF, dE/dx and Silica aerogel
Cherenkov counter. Each device covers different momentum range
for K/pi separation. Currently the Kaon identification efficiency of
more than 87% with 8% pion contamination is obtained by this system.
In order to cope with the KEKB upgrade in 2006, some R&D works
have been already started for a better PID system.
A Time-of-Propagation (TOP) counter and an aerogel-RICH counter are possible
candidates. Some beam test results of these devices will be presented.