Definition 1. If (?)A∈AI, the zero solution of(1.2 )is absolutely stable, then we say the interval system (1.1)is Robust absolutely stable, which is denoted by (1.1)∈RAS. Definition 2. If (?)A∈AI, the zero solution of (1.2) is absolutely stable for partial variables xj0, …, xn+1, then we call the interval system (1.1)Robust absolutely stable for partial variables xj0, …, xn+1, which is denoted by (1.1)∈RAS (j0→n+1).