The control of combustion development on spark ignition engines is one of the most important international topics under research today.Engines with high compression ratios have higher thermal efficiency than their similars with low compression ratios but have bigger restrictions on cycle-to-cycle variations and knocking.The monitoring of combustion process is a tool that allows for operating these engines with safer conditions and improving their availability through time.This paper shows the implementation of a combustion monitoring system on a natural gas fuelled spark ignition engine with high compression ratio using ionization current sensors.The implemented methodology consisted of measuring chemical and thermal current ionization from natural gas combustion using the ignition spark plug.The experiments were performed at several power outputs and spark advances.The results obtained from the ionization current system was compared with combustion analysis achieved from in-cylinder pressure measurement with piezo-electric sensor (traditional measurement system).This methodology shows results consistent with those reported in the state of the art and it shown to be a reliable tool for the combustion monitoring on these kinds of engines.