The Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 metal hydride electrodes were prepared at a pressure-holding time of t (t=10, 15, 20 and 25 minutes). The effects of the pressure-holding time on the activation performance, maximum discharge capacity, discharge potential characteristic and cycle stability of the electrode were investigated. The mechanism of the effects of the pressure-holding time on the electrochemical properties of metal hydride electrodes was also discussed in detail. The results show that the other electrochemical properties of the electrodes improve firstly and then degenerate with increasing pressure-holding time but to have no effect on the activation performance. The electrode at pressure-holding time of 15 min exhibits the best electrochemical properties. The improvements of the electrochemical properties are attributed to the increase of the charge-transfer reaction rate on the alloy and the decrease of the internal resistance of the electrodes.