Although it is important for baseball players to select a suitable bat to achieve higher performance in hitting motion, they usually select their bat depend on feeling and experience. We developed a bat select system for each player to select a suitable bat based on kinematic and kinetic parameters of the bat motion in swing movement. This system has two components ; such as, the instrumented bat for measuring bat motion under various inertial properties, and a selection algorithm to choose suitable bats based on kinematic and kinetic information of the bat. The bat contains accelerometers and gyroscopes in the bat handle end to measure kinematic parameters of the bat and a movable weight can be fixed at arbitrary position in the bat barrel to shift the center of gravity of the bat. And the other is software to select the suitable bat based on bat energy, swing time, bat head speed and apparent momentum of hitting point of the bat.