To investigate the components changing rule in epidermal mucus of discus fish (Symphysodon haraldi) during the breeding period, we measured the contents of cortisol, IgM, total protein, lactic acid and glucose in epidermal mucus. The results showed that the contents of cortisol, IgM, total protein, lactic acid and glucose in the epidermal mucus of S. haraldi were significantly influenced by fish gender, breeding period and there were significant interactions beteween gender and breeding period. In the free-swimming period of larvae, the contents of five components had significant difference between the female and male parent fish. When the discus fish began ‘lactating’, the components of epidermal mucus changed significantly, especially the male fish would secrete more nutrient and immune components for satisfying the needs of larvae.