Chrysanthemum-like Zinc Oxide (ZnO) nanorods was fabricated and characterized by hydrothermal route, the diamond was mixed to prepare electrophoretic fluid. After electrophoretic fluid was dispersed by ultrasonic cleaning machine, the coatings were deposited on titanium substrates. Field emission characteristics were tested after heat treatment. Results show that turn-on field of undoped diamond cathode is 7.3 V/μm and field emission current density is 81 μA/cm2 when electric field is set at 20 V/μm, while the doped samples show low turn-on field of 4.7~6.0 V/μm and high field emission current density of 140~158 μA/cm2. The reason is that after the interfusion of nano-ZnO, the electron transport capacity of coating is enhanced, the number of effective emitters increase and field enhancement factor β is improved. Because of diamond, the good bonding between coating and substrate is guaranteed after heat treatment and ohmic contact is formed, which reduces the thermal effect of field emission current. The stability of field emission current declines with the increasing amount of mixed ZnO. Both field emission current density and its stability should be considered, so mixing an appropriate amount of ZnO with nano-diamond can effectively improve field emission characteristics.