Abstract: The velocity distribution and resistance characteristics of unsteady laminar flow in plate channels were investigated theoretically and experimentally. Based on mathematical model of unsteady laminar flow, the influences of initial velocity distribution, pressure gradient rate and duration of acceleration (deceleration) on the instantaneous velocity distribution were analyzed. The results indicate that the velocity distribution of unsteady laminar flow is affected by channel size, fluid properties, pressure gradient rate and acceleration time. Under accelerated flow condition, the center fluid velocity is less than steady-state center fluid velocity, the flow resistance increases with the acceleration flow, and the deceleration flow is on the contrary. The results of experimental verification show that experimental data agree well with the result of theoretical analysis.