By using an abstract critical point theorem based on a pseudo-index related to the cohomological index, we prove the bifurcation results for the critical Choquard problems involving fractional p-Laplacian operator: (-) s p u = λ|u| p-2 u + |u| p * μ,s |x-y| μ dy |u| p * μ,s-2 u in , u = 0 in R N \ , where is a bounded domain in R N with Lipschitz boundary, λ is a real parameter, p ∈ (1, ∞), s ∈ (0, 1), N > sp, and p * μ,s = (N-μ 2)p N-sp is the critical exponent in the sense of Hardy-Littlewood-Sobolev inequality. These extend results in the literature for the fractional Choquard problems, and they are still new for a p-Laplacian case.