This paper describes the design and operation of a new diamond‐anvil press that can conduct x‐ray diffraction investigations of polycrystalline materials at sustained pressure and temperature up to 30 GPa and 500 °C. Several improvements have been made in heating efficiency, uniformity of temperature, alignment operation of anvil faces, and elimination of preferred orientation effect. Examples of the application to the study of a high‐pressure phase of phosphorus are shown.