The application of pump cavity in laser diode (LD) side-pumped laser head is introduced. By using ray tracing calculation, the effects of the pump cavity on the absorption efficiency and the intensity distribution of the pump light in the crystal were analyzed. The experiments were carried out respectively under the conditions of with and without pump cavity, with gold-plating pump cavity and with polished gold-plating pump cavity. The result showed that a gold-plating pump cavity greatly improved the output character of the pump head.