Black hole information paradox is a great thought experiment to deepen our understanding of quantum gravity, and recent gauge/gravity duality enable us to understand this problem from the dual gauge theory. In this talk, we present a N x N matrix model which is intended as a toy model of the gauge dual of an AdS black hole. By studying the Schwinger-Dyson equation of this model, we see how information loss is reflected as the decay of correlators at late time in our matrix model, which happens only at infinite N but never happen at finite N. We also discuss some implications for the information problem.