An improved process for the production of synthesis gas (or carbon monoxide and hydrogen) by oxidative conversion of natural gas or methane, which comprises passing continuously a gaseous reactant mixture comprising methane (or natural gas) and oxygen (or air) with or without water vapors over reduced or unreduced composite catalyst, containing non-transition and/or transition metal oxides, represented by the formula T.sub.m.sup.. N.sub.n.sup.. R.sup.. O.sub.p, wherein T is selected from Ni, CO, Ir or the like or a mixture thereof, m is T/R mole ratio, N is a transition or non-transition element selected from Ti, Zr, Hf, Zn, Mg, Ca or the like or a mixture thereof, n represents the N/R mole ratio, R is a rare earth element selected from La, Ce, Pr, Ho, Yb or the like, or a mixture thereof, O is oxygen and p is the number of oxygen atoms required to fulfill the valence requirement of the elements in the composite catalyst. Synthesis gas can be produced in high yields and with very high production rate by oxidative conversion of methane or natural gas to CO and H.sub.2 or synthesis gas, using the composite catalyst containing non-transition and/or transition metal oxides.