Abstract: The microstructure and properties of Ni based coating on Ti-6Al-4V alloys substrate fabricated by flames spray-welding and subsequently treated by medium-tempering were studied.The results show that a lot of hard particles are separated out after the medium-tempering treatment,which has the dispersion strengthen effect on spray-welded coating.After the medium-tempering treatment,the uniformity of coating's microstructure is improved,and the transition layer widens obviously;and the micro-hardness of coating changes more smoothly along depth direction,and the grads gradient of properties from soft substrate to hard coating decreases obvisously;and the micro-hardness of the spray-welded surface increases a little,but the wear loss of sample after tempering treatment is only equal to that of 1/2.33 of the before.