In this paper, we mainly study the stability of linear and interval linear fractional systems with time delay.
By applying the characteristic equations, a necessary and sufficient stability condition is obtained firstly,
and then some sufficient conditions are deserved. In addition, according to the equivalent relationship of fractional order systems with order
0<α≤1 and with order 1≤β<2, one may get more relevant theorems. Finally, two examples are provided to demonstrate the effectiveness
of our results