This work focuses on the diluent influence on stable methane flames in a fused silica micro flow reactor (MFR). Experimental and numerical investigations are performed. The first part presents the method of performing experiments and extracting data from an MFR in order to increase the reliability of the experimental results necessary for subsequent numerical simulations. Those methods are applied to premixed stoichiometric methane flames diluted by nitrogen, argon, helium and xenon. Methods to point out the influence of mixture thermodynamic and transport properties influence is presented. A numerical study of the influence of diluent on stable flames is also undertaken to support the experimental observations difficult to realize in such micro-devices.