Bubble motion in confined channels find applications ranging from carbon oxide sequestration to cardio-vascular embolism, and is ubiquitous in nature and industry. The confinement of bubbles in the channel causes the formation of a thin liquid film between gas and solid wall, whose flow field has been studied theoretically and especially for Newtonian fluids. Steadily moving bubbles in Newtonian fluids exhibits saddle shape. However, since a large amount of industrial and biological fluids are complex fluids, the motion of morphology of moving bubbles can be affected by non-Newtonian effect such as viscoelasticity. The purpose of this work is to explore the thickness distribution of liquid film between gas and solid wall during the motion of bubbles in a confined channel filled with viscoelastic fluid. In this study, bubbles are formed with flow focusing method of droplet microfluidics, bubbles move steadily through a long channel, and the film thickness is measured by an experimental method based on light interference. The relative optical interference intensity (ROII) method was used to obtain the thickness distribution of liquid film by analyzing the fringes. The thickness distribution of the liquid film within the bubble’s reference frame exhibits a different pattern compared to that in Newtonian fluids, and the symmetry of the spherical bubble is violated. This study provides experimental data for theoretical and computational research on bubble dynamics in confined channels.