Abstract: The single-crystal diamond films are grown by the microwave plasma chemical vapor deposition method,as well as the growth mechanism is studied.The experiments are performed in a quartz chamber microwave plasma chemical vapor deposition reactor.Three natural IaAB-type diamond substrates are nearly parallel to(111)-and(110)-oriented.The growth temperature is 800℃,the pressure is about 6 kPa and the growth time is about 8 hours.The surface morphologies of CVD single-crystal diamond films are observed and analysed by microscope and ESEM,which show the lateral growth forming the step-bunched surface——"step-flow".The CVD single-crystal diamond films are colourless and transparent.Under the same condition,CVD single-crystal diamond films grown on(111) direction show more orderly than that on(110).Moreover,the hydrogen concentration could influence the quality of CVD single-crystal diamond films.