There is an imperative need to explore new technologies for hydrogen energy production without sacrificing life and environment. A 27.12 MHz radio-frequency plasma in liquid was used to decompose cellulose suspension for hydrogen production. The experiment was conducted to investigate the effects of sodium hydroxide and ultrasonic irradiation pretreatment. Molar concentration of sodium hydroxide was varied to 0.001 M, 0.01 M and 0.1 M and ultrasonic irradiation time was varied between 15 and 60 minutes in order to observe the hydrogen production rate and hydrogen yield. Hydrogen production had no significant enhancement at lower than 0.01 M sodium hydroxide. On the other hand, the hydrogen production rate increased dramatically to 23.0 µmol/s at 0.1 M sodium hydroxide. Typical optical emission spectrum of 0.001 M sodium hydroxide solution showed that radical species including OH (281.1 nm), H_β (486 nm), H_α (656.3 nm) and O (777 and 845 nm) were generated which are very beneficial in attacking and decomposing organic molecules for hydrogen production. The highest production rate was obtained at 30 minutes of pretreatment. A longer than 30 minutes pretreatment with ultrasonic irradiation reduced the hydrogen production rate. Thus, ultrasonic irradiation pretreatment between 15 and 30 minutes was the potential condition for hydrogen production without sacrificing greenhouse gases effect.