The present work reports the facile synthesis of a planar heterostructure consisted of Sn3O4 nanosheet and 2-dimentional reduced graphene oxide (rGO) through microwave-assisted hydrothermal method (MHM). The planar heterostructure features with extended light absorption range and shortened charge transfer distance, and hence exhibits excellent photocatalytic activity and stability, with a hydrogen evolution rate of 20 mmol/g/h. The photoelectrochemical characterization shows that the planar heterostructure has better charge separation efficiency and interfacial charge transfer kinetics, which are also demonstrated by photoluminescence (PL) spectra and time-resolved PL decay analysis. It is found that the lifetimes of the photocarriers increased in the heterostructure. This work provides a new design of planar heterostructure for photocatalytic hydrogen generation through facile synthesis.