To establish the relationship between the microscopic chemical reaction mechanism and the macroscopic explosion pressure in the initial stage of methane explosion, the coupling relationship between content changes of key free radicals or molecules (such as CO₂, C₂, CHO•, OH•, C₃) and explosion pressure was investigated experimentally. The flame emission spectrum explosion pressure were obtained by a 20-Litre standard spherical explosion container and a grating spectrometer. Studies show that large amounts of CO₂ are produced during the pressure rising period, while the formation of C₂ and CHO• are primarily in the explosion induction period and they are consumed rapidly when explosion pressure rises. The content of OH• is at a high level throughout the methane explosion. The rapid increase of CO₂ accompanies with pressure rising, which reveals a positive correlation. On the contrary, the consumption of C₂ and CHO• accelerates when explosion pressure rises, revealing that they are correlated negatively. Formation reduction of C₂ and CHO• and their corresponding contents during the explosion induction period, suppression on OH• production during the whole methane explosion and decrease or inhibition in CO₂ formation can slow down or inhibit the explosion process and effectively reduce the methane explosion pressure. The result shows that it is possible to inhibit explosion and reduce the pressure efficiently through the manipulation of decreasing the production of C₂ and CHO• in the induction period, reducing the content of OH• throughout methane explosion and suppressing the formation of CO₂.