In this paper, we study the small time asymptotic behavior of the spectral heat content Q (α) D (t) of an arbitrary bounded C 1,1 domain D with respect to the subordinate killed Brownian motion in D via an (α/2)-stable subordinator. For all α ∈ (0, 2), we establish a two-term small time expansion for Q(α) D (t) in all dimensions. When α ∈ (1, 2) and d 2, we establish a three-term small time expansion for Q(α) D (t).