InAs(8ML)/GaSb(8ML) superlattice with p-i-n structure was grown on GaSb substrates by molecular beam epitaxy. The mid-wavelength infrared photodiodes with different area mesa was fabricated through standard photolithography, wet chemical etching and sputtered metal contacts. The passivation was finished by the anode sulphur technique and sputtered ZnS thin film. Compared with (NH4)2S solution treatment, the surface leackage currents density decreased three orders of magnitude and the R0A increased up to 103 times. The zero-bias resistance R0 was measured up to 106 ohms. The surface leakage current was not major dark current in photodiodes after the anode sulfur passivation. Capacitance-voltage relation showed that the background concentration in i layer was about 4~5×1014 cm－3. The property of the photodiode appeared no degradation after exposured in air for one month. It verified that anode sulphur passivation is an easy and effective technique.