The present invention relates to a process for preparing rice gruel in an aseptic package, whereby original soft texture and taste of grains of rice can be conserved or an extended period of time and protected from microbial contamination. The preparation process of rice gruel includes the steps of: rinsing raw ice and immersing the rice in water; putting the rice in a heat resistant plastic bowl and sterilizing at 130-150.degree. C. for 4-8 seconds four to ten times repeatedly; adding cooking water into the bowl in an aseptic space and cooking the rice; and sealing and wrapping the bowl. By adding the cooking water at two separate times, namely before the cooking process and the wrapping process, the liquid food's unique taste and texture can be maximized.