An inkjet amount measuring system, an inkjet amount measuring method and an inkjet amount controlling method. The inkjet amount measuring system includes: an inkjet printing spray head; and electricity applying device configured to apply electric charges to ink droplets passing through a nozzle of the inkjet printing spray head; a magnetic field generating device configured to generate a magnetic field to deflect the charged ink droplets; a test board having a surface for carrying ink droplets; and a processor configured to calculate an amount of ink droplets according to positions of falling points of the ink droplets on the surface of the test board, an electric charge amount of the ink droplets, and a magnetic field intensity.