Ultrasound grayscale B-mode imaging is the most frequently used modality for examining fatty liver. Different concentrations and arrangements of fatty droplets in the liver may produce different statistical distributions of ultrasound backscatter signals, which may be treated as a useful clue for assessing the stage of fatty liver. To verify this point, we investigate the relationship between changes in backscattered statistics and the concentration of fatty droplets in the liver. Fatty liver was induced in rats fed a methionine-choline-deficient diet. Livers were excised from rats for in vitro ultrasound scanning using a single-element transducer. The envelopes of the acquired raw ultrasound signals were used for the analysis of the backscattered statistics by ultrasound Nakagami parametric imaging, which has been shown as a reliable tool to model the statistical distribution of ultrasound backscatter signals. Histological analyses and the measurements of triglyceride and cholesterol in the rat liver were conducted for comparison with the Nakagami parameter. Results show that the ultrasound Nakagami parameter has an excellent correlation with the concentration of fatty droplets, demonstrating that ultrasound backscatter statistics depend on the degree of fatty liver in rats.