The coming of Software Defined Radio (SDR) redefines the way to implement transmitter. With the theory getting more matured and completed, SDR technology has been widely used in cellular communication system as well as other civil and military wireless communication systems. As one of the core technologies of SDR, direct-up converted transmitter is also getting more and more extensive application.The algorithms on the multi-velocity signal processing and digital filter design has been studied in this paper. The block diagram of the transmitter has been put forward at first. Then some high efficient digital filters have been studied and realized. Based on the specifications, a transmitter which used direct-up conversion architecture is achieved by interpolation with anti-aliasing filters, such as raised cosine filter, half-band filter and cascaded integrator comb filter. In addition, it finishes the Kaiser widowed half-band filter. Sub-module interpolation filters in the transmitter which used direct-up conversion architecture has been simulated. Analysis and estimation of the resource has been made too.At last, based on the characteristic of these filters, the design of filters for the transmitter which used direct-up conversion architecture has been implemented by cascading these three kinds of filters, using a new method for designing filter which can reduce the resource usage with a low cost. Comparing with a traditional method, an effective way has been proposed to reduce sideband interference and local oscillator leakage in the transmitter which used direct-up conversion architecture that has been efficiently used in engineering practice.