In this study, we used OH/HCHO simultaneous PLIF measurement for qualitative evaluation of heat release rate. The effects of the wall on flame curvature and heat loss are investigated. The propane- and methaneair premixed gas are considered. It is shown that the preheat effect is more significant than Lewis number effect due to flame curvature for the maximum value of heat release rate. The heat loss to downstream stagnation plate is also effective for heat release rate in the condition that there are flame front near the stagnation plate.