As　the　enhanced　mobile　broadband　technology　is　commercially　deployed　in　a　growing　number　of　regions,　there　is　a　gap　between　5G　millimeter　wave　frequency　bands　and　high　efficiency　and　high　gain　antennas.　This　paper　presents　a　design　of　a　microstrip　patch　antenna　array　with　RT　Rogers　5880　substrate　that　operates　in　the　n257　channel,　which　has　an　operating　frequency　of　28　GHz,　and　has　a　bandwidth　of　400　MHz.　The　parameters　of　the　single　elements　are　derived　from　the　result　of　theoretical　calculations.　The　performance　of　the　single　element　is　simulated　by　CST　and　evaluated　to　instruct　the　refinement　of　the　parameters.　After　the　design　of　the　single　element　of　the　microstrip　patch　antenna,　the　design　of　the　microstrip　patch　antenna　array　is　proposed.　It　is　also　refined　according　to　the　evaluation　of　simulation　results.　The　finalized　patch　antenna　array　design　fed　by　a　50　ohms　system　has　a　realized　gain　of　13　dBi　and　3dBi　angular　width　of　15.8　with　a　working　efficiency　of　88%　while　operating　at　28GHz　with　a　bandwidth　of　500　MHz.　Moreover,　compared　to　single　patch　antenna,　the　patch　antenna　array　features　in　high　spectrum　effectiveness,　high　community,　and　can　be　applied　to　multi-beam　antenna　system.　It　also　small　and　reasonable　in　cost.　It　has　high　potential　to　replace　the　single　patch　antenna　in　the　area　of　mobile　communications,　satellite　communications　and　global　positioning　systems　and　complement　with　5G　technology.　©　2022　SPIE.