This work presents a numerical and experimental study in a laboratorial rig to measure local flame temperature and alkali emission during the combustion of sugarcane bagasse and straw. Tubular combustion chamber to simulate combustion in grate is used. A spectral analysis method in the visible spectrum was used for measurement of local temperatures in a sugarcane bagasse flame and sugarcane straw flame. The two-color method is used to calculate flame temperature. In flame reactive zone, the bagasse and straw flame temperatures in the range of 1420 to 1510 K and in the range of 1450 to 1550 K respectively are calculated. The intensity of alkali emission during the sugarcane bagasse and straw combustion is calculated using data of the spectrum in visible range. It was found that potassium emission is correlated with the instantaneous bagasse flame temperature in the reactive combustion zone. Emission of potassium and sodium during straw combustion is higher than in bagasse combustion. Temperature and alkali emissions along the flame height are measured.