The observation of micro-jet flame shape and measurements of important radicals in micro-jet flame are of great significance to the research and development of micro energy and power system based on combustion characteristics of micro-jet flames. In this work, an optical measurement system of mcro-jet flames was established experimentally to study micro-jet flames using H2 and CH4 as fuels and to measure the spatial distribution of two important radicals, CH and OH. Firstly, the effect of exposure time of camera on images of the H2 micro-jet flames was explored, obtaining the variation of micro-jet flame shape under different flow velocities. Then, the Laser Induced Predissociative Fluorescence (OH-PLIF) technique was applied to obtain the distribution of OH radical in H2 and CH4 micro-jet flames under different fuel flow velocities, meanwhile, a Digital Single Lens Reflector (DSLR) plus a CH filter with a long time exposure (30 s) was employed to obtain the distribution of CH radical in CH4 micro-jet flame. The results showed that, the clarity of flame image is promoted as the exposure time increased and a clear image of H2 micro-jet flame is acquired when exposure time is 30 s; a clear image of distribution of OH radical in micro-scale flames is captured via an ICCD camera with a resolution of 2 048×2 048. The experimental results indicate that the numerical computation of micro-jet flame shape and important radicals is accurate and reliable.