Friction drag and characteristic of bubbles in horizontal water channel are investigated at bulk liquid velocity Um = 1 ∼ 5 m/s (Reynolds number Rem = 16,000 ∼ 120,000 (based on the channel height)) and mean void fraction α = 0.5, 1, 2 %. Firstly, shear stress sensor is applied to investigate the relation between friction drag with bubbles and bulk liquid velocity. Friction drag in the bubbly flow is larger than it in the single-phase flow at Um = 1 ∼ 2 m/s. It in the bubbly flow, however, decreases with the mean liquid velocity. Furthermore, it in bubbly flow is smaller than it in the single-phase flow at Um ≥ 3 m/s. Secondly, fiber optic sensor is applied to investigate the void fraction distribution, bubble diameter distribution and streamwise velocity of bubbles. The peak value of the void fraction decreases with increasing of the bulk liquid velocity at Um = 2 ∼ 5 m/s. Bubbles exist in only y/δ = 0 ∼ 0.5 at Um = 1, 2 m/s. The mean bubble velocity increases with the bulk liquid velocity. The mean Sauter diameter decreases with increasing of the bulk liquid velocity. It appears that the high void ratio near the wall causes the increasing of drag and friction drag decreases when bubbles exist in whole of upper half of channel.