In this paper, a novel X-ray tube, which uses a photocathode as an electron emission source, is first introduced. The X-ray tube with photocathode can use an external light source to control the output of photoelectrons, thereby controlling the characteristics of the emitted X-rays. Compared with the traditional X-ray tube with hot cathode, the X-ray emitted by the photocathode X-ray tube is completely modulated by the external light source. Therefore, X-rays can achieve instant on-off and arbitrary pulse waveform emission, and have extremely high time resolution. The basic characteristics of the photocathode X-ray tube was tested. By using the developed X-ray tube and LED light source, preliminary X-ray communication experiments have been carried out. The results show that the digital signal restoration with a frequency of up to 1MHz can be achieved. Except for X-ray communication, the developed photocathode X-ray tube can also have important applications in many fields such as radiation calibration and scintillator afterglow measurement. © 2021 SPIE