Drying characteristics of horse mackerel drying in a heat pump dehumidifier (HPD) were studied. Quadratic orthogonal regression design was employed to establish the connection between modeling coefficients (K and n) and temperature and velocity. The experimental data were analyzed with statistical method and a mathematical model was established. The obtained mathematical model suitable for horse mackerel drying by HPD is Page model. There were few differences between the speculated result and the calculated value. Therefore, mathematical model established on these data could be used to describe the heat pump drying process of horse mackerel.