Lean premixed flame characteristics of several typical low calorific value (LCV) syngases (basis CO/H-2/CH4/CO2/N-2), including bituminous coal, wood residue, corn core, and wheat straw gasification syngas, were investigated using OH planar laser induced fluorescence (PLIF) technology. OH radical distributions within the turbulent flame were measured for different turbulence intensities. Flame structures of syngases were analyzed and characterized with respect to burnt and unburnt regions, flame curvature (sharp cusp), local extinction (holes and penetration), OH reaction layer thickness, wrinkling, and other features, with OH-PLIF instantaneous images and statistical analysis. Results show that H-2 content, LCV, and turbulence intensity are the most effective factors influencing the OH radical intensity and thickness of OH radical layers. The bituminous coal gasification syngas with relatively higher LCV and H-2 content tends to burn out easily. Through changes in thickness of the OH radical layers and signal intensities, the reaction layer can be compressed by intensifying turbulence and thereby the combustion processes of syngas.