Abstract. Supersonic molecular beam injection (SMBI) has been successfully developed and used in HL-1M and HT-7. SMBI can enhance the penetration depth and fuelling efficiency. It can be considered a significant improvement over conventional gas puffing. The recent beam injection experiments have been carried out by increasing the pressure of the beam source from 0.5 MPa to 1.0 MPa or higher for enlarging the characteristic dimension of the supersonic area and avoiding the emergence of Mach shock before the beam arrives the HL-1 M plasma. The hydrogen clusters may be found in the beam produced by high working gas pressure according to the Hagena empirical scaling. The hydrogen particles of the beam have penetrated into the plasma center region, in which the average velocity of the injected beam is over 1200 m/s. The plasma density increases step by step after multi-pulse SMBI, just as the effects of multi-pellet fuelling. The increase rate of electron density approaches that of the small ice pellet injection (PI). A comparison of fuelling effects was made between SMBI and small ice PI in the same shot of ohmic discharge in HL-1M.