Bubble uniformity of Taylor flow in a T-Hunction microchannel characterized by the bubble length variation coefficient (CVb) was studied via both experiments and theoretical derivations. On the one hand, the correlation between bubble uniformity and the Capillary number (Ca) ranging from 0.00027 to 0.0071 was established at operating conditions with different flow rates of gas and liquid and various liquid phases. A sudden increase of CVb was observed when the value of Ca was below a certain threshold indicating compromised bubble uniformity. Pressure sensors and a high-speed camera were used to analyze the causes of such a phenomenon by monitoring the bubble breakup process at outlet. As Ca was smaller than 0.0008, bubble breakup generated a large pressure variation which seriously affected the gas flow rate and bubble uniformity. On the other hand, a pressure model was derived to quantize pressure variations and to estimate CVb, which were validated by experimental data and showed promising performances. Moreover, the model for calculating CVb, can also be used to optimize operating condition and ensure the bubbles uniformity. (C) 2015 Elsevier Ltd. All rights reserved.