A L–mode scaling law of global energy confinement time in ion cyclotron resonance heating (ICRH) is proposed in this paper. The scaling is based on 292 observations from tokamaks PLT, JET, ASDEX, TEXTOR, JFT–2M and JIPP T–IIU. The regression analysis reveals the scaling being of the form: τE α a-0·18 R1·27 IP0·98 BT0·10 K0·20e0·12 Ptot-0·51. Comparision with other scaling laws and fitting the scaling law to the theoretical constraint model have shown many physical phenomena of ICRH wave damping mechanism. To reach the ignition condition, some modifications of experimental technique and tokamak configuration are needed to enhance the energy confinement time.