Objective This study focused on the effects of different enrichment designs on behavior and cortin levels in male SD rats. Methods Forty-five 6-week-old male specific pathogen free SD rats were randomly divided into four groups. The single cage group had nine rats and the other three groups each had 12 rats. The novelty group was housed in a composite environmental enrichment scheme composed of nesting material, shelter, grinding rods, and a new scheme was provided every week. The environmental enrichment group provided one kind of material every week. The control group and the single cage group did not receive enrichment. The experiment lasted 9 weeks. Behavior was sampled using instantaneous scanning sampling method. Serum and urine adrenocorticotropic hormone (ACTH) and corticosterone (CORT) levels were measured. Results Novelty group rats exhibited more exploring behaviors than rats in the other groups. Rats of the single cage group increased their inactive behavior. No significant differences were found among groups in the serum levels of ACTH or CORT. However, in urine, the concentration of ACTH and CORT showed the following trend: novel grouP>single cage grouP>control grouP> environmental enrichment group. Conclusions Single cage housing inhibits the expression of behaviors in SD rats, which is detrimental to their welfare. However, the complex novel enrichment program increased positive behaviors, such as exploration behavior and also has an effect on adrenocortical hormones. In practice, simple and practical environmental enrichment materials and schemes should be selected according to specific housing conditions.