The invention discloses an ultraviolet broadband tuning frequency conversion method, an ultraviolet broadband tuning frequency conversion device and an ultraviolet broadband tuning frequency conversion laser, which are characterized in that a nonlinear optical crystal through which ultraviolet penetrates is cut along a certain direction, and phase gratings periodically arranged in an ordered region and a disordered region are processed in the crystal in an ultrafast laser photoetching form; the effective period length of the phase grating is changed by controlling the incident angle of the fundamental frequency light or the temperature of the nonlinear optical crystal, so that the phase difference between the fundamental frequency light and the frequency doubling light or the sum frequency light is adjusted to provide tunable phase compensation, the phase matching condition is met, phase matching in multiple polarization forms can be achieved at the same time, and the polarization effect is improved. Therefore, the ultraviolet broadband tuning frequency conversion is realized, and wavelength and power detection is facilitated; the invention provides a new way for ultraviolet broadband optical frequency conversion, gets rid of the limitation that traditional phase matching depends on a specific polarization direction, makes full use of the pump light source, and has the advantages of high output power, wide tunable wavelength range, no polarization limitation and the like.