Carbon nanotubes (CNTs) is a kind of prosperous field-emission material. It can be made as field emission cathode of X-ray source. In experiments, CNTs using as cathode is printed on glass base, the anode was made of Cu and processed to a cylinder with one end made to a hemisphere whose radius is 2 mm. High voltage supply are tunable in the range of 0～19 kV. X-ray source is stably runing for four hours at work vacuum of 1×10-4 Pa. At last, kα line spectrum is detected by the flow-gas proportional counter. The experimental results reveal that the emission of X-ray source are stable and CNTs is well fitted to X-ray source cathode. The fitful structure of field emission X-ray source was given out in the end.