Abstract: The effect of the tube making Technique on the photoemissive property of the photocathode is described.The technical quality of the cathode assembly preparation and the cathode activation is detected on line with the analytical instruments and the method of optical detection.The result shows that the main factors,which affect the technical quality of the cathode assembly preparation,are surface oxidization of emissive layer,impurity pollution,doped concentration nonuniform,less variation of doped concentration gradient,the sticking stress of GaAs and glass,and the main factors,which affect the cathode activation,are the degree of vacuum for activation at lower than 8x10-8Pa,the partial pressure of H2O,CO,CO2 and C in the vacuum residial gas at higher than 10-8 Pa and the improper caesium and oxygen refining.With a method of the transmission-reflection luminance,we also found that the pinholes,cracks and atomization on the surface of the emissive layer are the key factors that might cause the lower emissive property of the photocathode.