import arcpy
geojson = {"type":"Polygon","coordinates":[[[120.81878662109375,44.54437255859375],[120.74359130859375,44.54150390625],[120.769775390625,44.599365234375],[120.8216552734375,44.64581298828125],[120.87115478515625,44.5936279296875],[120.81878662109375,44.54437255859375]]]}
geom = arcpy.AsShape(json)