Abstract: Experimental studies of single-phase flow characteristics in rolling plexiglass rectangular channel with the hydraulic diameter of 5.58 mm were carried out using de-ionized water as the working fluid under normal temperature and pressure. The results show that the friction coefficient in rolling condition fluctuates with time and the period is equal to that of rolling movement. The smaller the Reynolds number is, the smaller the rolling period is, and the greater the maximum rolling angle is, the greater the fluctuations in amplitude of the friction coefficient are. An empirical correlation for the transient friction coefficient under rolling conditions was obtained by applying π theorem and fitting a large number of experimental data.