Abstract: In this work, we studied factors affecting the end effect in microtubes by conducting nitrogen microscale flow experiments in 31~100 μm tubes under the conditions of 5~20 MPa and 25~60℃. We proposed the double tube-length differential pressure calculation method for end-effects induced additional differential pressure Δp_end. Using this method, it is found that there is a negative correlation between Δp_end and tube diameter d, and Δp_end increases monotonically with the flow velocity v. The effect of pressure on Δp_end is not significant under low flow rate conditions, however Δp_end increases with increasing pressure under high flow rate conditions. Under the experimental conditions in this paper, temperature has little effect on Δp_end. Finally, we established an empirical model to describe the relationship between Δp_end and v, d.