Coal structure and reaction conditions are the main factors influencing coal pyrolysis reactions. To investigate the pyrolysis characteristics of coals with different metamorphic degrees, three typical coal samples (lignite, bituminous coal, and anthracite) were selected as research objects. Thermogravimetric analysis experiments were conducted under four heating rate conditions to analyze the pyrolysis behavior of coals under different reaction conditions. The evolution of functional groups was analyzed by in-situ infrared test. The change law of reaction activation energy was calculated by the modified Kissinger-Akahira-Sunose (KAS) method. The results showed that the reaction behavior of coal at different temperatures can be divided into the water evaporation stage, gas desorption stage, slow decomposition stage, rapid pyrolysis stage, and condensation stage. The greater the degree of metamorphism, the higher the characteristic temperature and the lower the reaction degree. The pyrolysis temperature difference between anthracite and lignite reached 104.3℃. At 1000℃, the residual masses of the three coal samples were 58.19%, 65.90%, and 89.49%, respectively. The heating rate primarily influences the degree of reaction in coal samples at specific temperatures, without fundamentally altering the reactions that may occur during coal pyrolysis. A higher heating rate results in a narrower and sharper differential thermogravimetry (DTG) peak, accompanied by a lower reaction extent at the same temperature. After entering the pyrolysis stage, the activation energy for lignite and bituminous coal exhibits minimal variation, remaining at approximately 210 and 255 kJ/mol, respectively. Anthracite exhibited a high degree of aromatic ring condensation, molecular symmetry, and low reactivity. Its functional groups demonstrate low absorbance and exhibit delayed response patterns relative to other coal samples. Upon entering the pyrolysis stage, it must overcome a higher reaction energy barrier to sustain the reaction.