For the profound comprehending of Gibbs function and conditions of phase balance, the paper deduces one of the phase balance conditions is the chemical potential being equal in different phases.

• 通过对吉布斯函数定义的再认识和单元两相系平衡条件的推导得出单元复相系相平衡的条件之一是具有强度性质的各相化学式相等。