The well-posedness of weak solutions to a double degenerate evolutionary p(x)-Laplacian equation u t = div(b(x, t) ∇A(u) p(x)-2 ∇A(u)), is studied. It is assumed that b(x, t)| (x,t)∈Ω×[0,T] > 0 but b(x, t)| (x,t)∈∂Ω×[0,T] = 0, A (s) = a(s) ≥ 0, and A(s) is a strictly monotone increasing function with A(0) = 0. A weak solution matching up with the double degenerate parabolic equation is introduced. The existence of weak solution is proved by a parabolically regularized method. The stability theorem of weak solutions is established independent of the boundary value condition. In particular, the initial value condition is satisfied in a wider generality.