Core-collapse supernova marks the death of massive stars with a zero-age-main-sequence mass of about 8-100 solar masses, and is one of the most important objects in modern astronomy. The ability to emit gravitational waves, neutrinos, and electromagnetic waves makes core-collapse supernovae excellent targets for multi-messenger astronomical surveys. In this talk, I will present the consequences of a first-order QCD phase transition in core-collapse supernovae, studied with state-of-the-art two-dimensional hydrodynamic simulations. In particular, I will talk about how the detection of multi-messenger signals can probe the phase transition and provide important information on supernova physics.