The invention provides plant fiber diatom ooze and a preparation process thereof. The plant fiber diatom ooze comprises the following components in mass ratio: 10-40% of diatomite, 10-50% of plant fiber powder, 5-20% of kaoline, 1-5% of bentonite, 3-10% of anion powder, 3-10% of titanium dioxide, 3-10% of imidoketone, 5-25% of calcite powder, 5-25% of ash calcium, 5-25% of redispersible latex powder, 0.2-0.5% of powder defoaming agent, 0.2-0.5% of powder wetting agent, 0.2-0.5% of powder mildew preventive and 0.2-5% of hydroxypropyl methyl cellulose. By utilizing techniques of sorting, mixing, screening and the like, the produced diatom ooze has excellent elasticity and sound-absorption heat-insulating performance, soft and comfortable touching sense, and crack resistance and mildew resistance, and the produced diatom ooze is an indoor decoration wall material which has excellent combination performance integrating functionality, practicability and decorative performance.