Droplet spreading characteristics on substrate make great effect on inkjet printing quality, but the ink viscosity, substrate surface parameters all and droplet flying velocity all affect droplet spreading on substrate. In this paper, we just research on droplet spreading on Substrate been influenced by droplet flying velocity from inkjet print-head to substrate. We set up numerical model of flying droplet based on moment equation and energy conservation equation, so that we can get theoretically result, then keep ink viscosity and substrate surface parameters invariableness, just change the droplet flying velocity, and from the analysis result, we find the relationship between droplet flying velocity and droplet spreading characteristic. From the experiment result, we amend the model for droplet, so that we get a correct numerical model for droplet spread, and in this model droplet velocity is the only variable.