Objective To establish normal range and mean values of blood biochemical measurements in SPF SD rats used in long-term toxicity test. Methods Blood samples were taken from SPF SD rats in different age and sex. A number of blood biochemical parameters were measured using an automatic biochemical analyzer. Results Normal range and mean values of all data were obtained. Most biochemical values were influenced by age and sex of the rats. The variations of TBil, ALP, TG in rats of different sex and ALP, CK, TG, CHO in rats in different age showed a clear regularity. Conclusion It is inappropriate to combine the biochemical data obtained from female and male rats together for statistical analysis in long-term toxicity test. Attention should be paid to the influence of age and sex of rats when biochemical data collected in an experiment are compared with normal values and ranges.