Taking grass carps with the initial weight of about 20 g as the research object, the basic feeds of grass carps were added with 0.0%, 0.1%, 0.3%, 0.6%, 0.8%, and 1% of nano-sustained release sodium butyrate to prepare 6 types of experimental feeds with equal nitrogen and energy. The effects of different concentrations of nano-sustained release sodium butyrate were surveyed on growth and intestinal cell proliferation of grass carps. The experiment was carried out in cages with 50 carps per cage, and each treatment was repeated 3 times for 60 days. Experimental results indicated that the addition of nano-sustained release sodium butyrate significantly promoted the growth of grass carps and significantly increased the ratio of intestinal villus to crypt depth. When the addition of nano-sustained release sodium butyrate was 0.6%, the weight increase rate, specific growth rate, fullness and intestinal villus height of grass carps were the highest, which was significantly higher than that of the control group (P <0.05). The study results indicated that addition of appropriate amount of nano-sustained release sodium butyrate can promote the growth of grass carps through increasing the intestinal villus height, and the suitable addition dosage was 0.6%.