Objective To evaluate the acute toxicity and mutagenicity of hydrogenated dimer acids. Methods A total of 20 SPF KM mice were selected for acute oral toxicity test.The mice were poisoned with a single administration of 0.2 mL/10 g body weight.The toxic behavior and death of mice were observed within 14 days after being poisoned,depend on which the median lethal dose (LD₅₀) and the acute toxicity was calculated and classified,respectively.40 SPF KM mice were selected for the mammalian erythrocyte micronucleus test.The mice were randomly divided into three groups:experimental group (group 1 and group 2),negative control group (corn oil) and positive control group (cyclophosphamide,40 mg/kg) .After oral poisoning with a single gavage,the bone marrow samples were taken at 24 h and 48 h in the experimental group,the same kind of samples were taken at 24 h in negative and positive control groups.After slide preparation,the counting area were selected with intact cells of proper distribution and coloration,inside which,the numbers of polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) in 200 red blood cells were counted,then the ratio of PCE to NCE was calculated.The number of micronucleus-containing PCE was counted in 2 000 PCE,and the micronucleus rates were calculated.The ratios of PCE/NCE and the micronucleus rates were compared by chi-square test. Results The acute oral LD₅₀ of hydrogenated dimer acid in mice was more than 5 000 mg/kg .There were no significant differences in PCE/NCE ratios and micronucleus rates between the experimental groups and the negative control group in male and female mice(P＞0.05). Conclusion Hydrogenated dimer acid is a substance of low toxicity and no mutagenic effect was found.