Swirling flow is widely used in gas turbine burners to promote fuel/air mixing uniformity and to stabilize lean premixed flames. In this study, numerical and experimental methods are utilized to investigate the effects of burner geometry on fuel/air mixing and combustion performance and to optimize the burner geometry. The premixed burner geometry parameters including air swirling angle and fuel injection diameter/angle are modified to achieve fuel/air mixture uniformity. Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) are adopted to examine the flow field, Planar Laser Induced Fluorescence (PLIF) for detecting OH radical distribution thus investigating the characteristics of the reaction field. Burners of different configurations are manufactured to conduct combustion experiments. The burner with the worst mixing performance can‘t ignite successfully. However, burners with better mixing performance have a homogeneous reaction field with less perturbance, and the NOX emission stays at a relatively low level around 2.5 ppm (15% O2) at the designed operating condition.