Objective Evaluation of Pentoxifylline（PTX）therapy for nonalcoholic steatohepatitis(NASH) in rats by high frequency ultrasound. Methods Sixtyeight SD rats were randomly divided into normal control (18) and experimental groups (30) were feed by highfat diet. and therapy groups (20) in 8 and 12 weeks were given the PTX for 4 weeks. Results Fat degeneration commenced after 8 weeks of highfat diet. The liver enlarged, the edge of the liver became dull, the echo enhanced, and the vessels became indistinct. Those were more marked after 12 weeks. In pathological images, the simple fatty livers were observed in the model group at 8 week. From 12 weeks to 16 weeks, the liver gradually progressed from nonalcoholic steatohepatitis (NASH) to liver fibrosis. The changes exhibited little in therapy groups. There were significant differences of ultrasound and pathological features between control /experimental and therapy group（P<0.05）. C