Abstract: The effect of u and d quark mass on the conversion of the two-flavor quark matter to more stable strange quark matter has been analyzed.It is shown that the u and d quark mass has slight influence on equilibrium parameters,involving quark temperature,quark abundances and total neutrino energies.So the u and d quark mass can reasonably be neglected when the conversion processes are studied in a supernova core.It further indicates that the u,d quarks are not good quantum transition flavors and the structure of photon comprised of quarks is also supported.