The invention discloses a method for improving the threshold voltage distribution of a device, comprising the following steps: the first step, core NMOS halo ion implantation and LDD ion implantation; the second step, I / O NMOS LDD ion implantation; the third step, LDD fast Thermal annealing, the temperature of the rapid thermal annealing is 950° C.; the fourth step, core PMOS halo ion implantation and LDD ion implantation; the fifth step, I / O PMOS LDD ion implantation. The method of the invention can greatly reduce the fluctuation of the NMOS threshold voltage with the length of the channel, thereby increasing the process window and improving the characteristics of the device. The invention is applicable to the NMOS device manufacturing process in the semiconductor manufacturing process.