The control of electrostatic charge on particles in gas-solids pipe flow has been studied experimentally and theoretically. Alumina particles of 3.3 mu m in count median diameter were dispersed in airflow and pneumatically transported in the dilute phase. Five different materials were used for the transport pipes, and the relationships between the particle charge and the pipe length were obtained. The polarity and the amount of particle charge were found to depend on the pipe material and the length. In order to control the particle charge, a system combining two different pipe materials was proposed depending on the particle-charging characteristics. The charge controlled by this method was in good agreement with the theoretical calculation. furthermore, it was found that the distribution of particle charge as well as the average can be controlled.