The objective of this study is to develop a new prediction method of frictional pressure drop inside horizontal mini-channels for condensation process. Based on the database containing wide range of experimental conditions on the kinds of refrigerants and mini-channels, we developed a new frictional pressure drop correlation of HFC and HFO refrigerants condensing in mini-channels. The present correlation agrees well with experimental data of condensation flow, and it also agrees with the data of two-phase adiabatic flow in mini-channels.