We propose a highly tunable 100% spin-polarized current generated in a spintronics device based on Dirac semimetal under a magnetic field, which can be achieved merely by controlling electric parameters, i.e. the gate voltage, the barrier in the lead and the coupling strength between the leads and Dirac semimetal. These parameters are all related to the special properties of Dirac semimetal and Weyl semimetal. The spin polarized current generated by gate voltage is guaranteed by its semimetallic feature, because of which the density of state vanishes near Dirac nodes. The barrier controlled current results from the different distance of Weyl nodes generated by the Zeeman field. And the coupling strength controlled spin polarized current originate from the surface Fermi arcs. All these features make a great potential to realized Dirac semimetal based spintronic devices.