Tetrapod-shaped ZnO nanomaterial field emission cathode was preparated by deposition method. To the high-vacuum flat capsulation with phosphor screen and cathode was applied a voltage to test the cathode emission current and the phosphor screen brightness. For the cathode with total area 13×15 cm2, the test results showed that when the volume percentage of K2SiO3 ranged from 50 × 10-3 to 83× 10-3, concentration of Ba(NO3)2 arranged from 50 × 10-4 to 77×10-4 M, and concentration of tetrapod-shaped ZnO arranged from 82×10-4 to 12×10-3M, the cathode emission current was the largest, and phosphor screen at peak brightness could reach 60 cd/cm2 The average brightness was 48 cd/cm2