This paper devotes to the study on the stability and decay of solution to fractional differential system involving the
ψ
-Hilfer fractional derivative of order
α
∈
0,1
and type
β
∈
0,1
. We first derive the solution of linear system by using the generalized Laplace transform, which can be represented by the form of Mittag-Leffler function. Then, in terms of the asymptotic expansion of the Mittag-Leffler function, stability properties of linear system are analyzed in more detail. Finally, we construct a linearization theorem and determine the stability near the equilibrium for the autonomous nonlinear differential system with the
ψ
-Hilfer derivative.