Five coal chars were prepared in a flat flame flow reactor (FFR) which can simulate the temperature and gas composition of a real pulverized coal combustion environment. Reactivity of these chars with NO in the temperature range of 1273-1573 K has been characterized by experiments in a high-temperature drop tube furnace (DTF). Two normalized parameters ((X) over bar and m(c)) are proposed to analyze the effect of inherent metal content on char reactivity. The inherent metal catalysts in chars, such as magnesium, potassium, sodium, calcium, and iron, can significantly increase reactivity of char by reducing the activation energy. The reactivity of NO-char reaction increases with m value monotonously and linearly in a certain range. Experimental results showed that the catalytic activity of magnesium, potassium, sodium, calcium, and iron at the temperatures of 1273-1573 K were in decreasing sequence. In this study, the magnesium, which was rarely studied in other literature, appears to have a great catalytic effect on the reduction of NO by chars.