Graphene has received great interest because of its peculiar band structure and excellent physical properties. But today, the development of graphene is limited to its size and quality. In this paper, single- and multilayer graphene films were synthesized on copper foils by chemical vapor deposition(CVD) using methane at ambient pressure. Experiment results find the high temperature, low concentration of methane gas, shorter growth time and suitable gas flow are the key to get high-quality and large-scale graphene films. Raman spectra, scanning electron microscope(SEM) and transmission electron microscope(TEM) characterization indicate the graphene films are mostly single-layer, only with rare area having multilayer around copper boundaries. Further electrical tests show the graphene films grown by CVD method represent semiconductor behaviors under low temperature and the sheet resistance of graphene films is decreasing with the external magnetic field increasing.