A large plasma sheet with a size of 60 cm60 cm2 cm is generated in an apparatus with a hollow cathode. The electron density distribution of the large area plasma sheet is measured. Since the duration of high voltage pulse is short, we change measurement methods. Besides, modification is used for electron saturation current to get the real density. The two-dimensional electron density and electrical field distribution are calculated at discharge currents ranging from 1 to 6 A. Meanwhile we discuss other parameters related to density distribution. The electron density distribution is important for plasma sheet to steer microwave. It is encouraging that the large area plasma sheet generated by the hollow cathode is uniform and has sufficient electron density to reflect X-band (812 GHz) microwaves.