Millisecond pulsars (MSPs) are fast spinning neutron stars with spin periods of a few milliseconds, that have been confirmed by the Fermi LAT as a class of gamma-ray emitters. During over four years of operation, Fermi LAT has detected over 30 MSPs, these gamma-ray emitting MSPs can be found in various environments (e.g., globular cluster, galactic field). By studying the gamma-ray properties of MSPs in different environments, we can have a better understanding on the recycling process of MSPs formation as well as the emission mechanisms. We present our latest findings on gamma-ray emitting MSPs in the Fermi era.