A moiré superlattice can be formed by overlaying two atomically thin van der Waals materials with a rotation angle or with a lattice mismatch. Since the discovery of correlated insulators and superconductivity in magic angle twisted bilayer graphene, constructing moiré superlattices by various two-dimensional (2D) van der Waals materials and studying their novel properties emerge as a hot topic and research frontier in condensed matter physics. Here we review the recent experimental progress of 2D transition metal dichalcogenide moiré superlattices. In this system, the formation of moiré flat band does not rely on certain magic angles. Experimentally, a series of correlated electron states and topological states have been discovered and confirmed. Further theoretical and experimental studies can find a wealth of emergent phenomena caused by the combined influence of strong correlation and topology in transition metal dichalcogenide moiré superlattice.