Abstract: LTE-A is becoming the standard of 4G with its perfect performance.However,LTE-A demands that the transition band should be very narrow and the ripples in pass band should be very low in the front digital filter.To meet the demands,this paper proposes a design method for the digital filter,using a frequency-response masking technology with optimization of the inserting gene M,the length of the filter and the range of the ripples.Simulation results show the complexity are 68,79,87,87,87,and 87,when the bandwidth are 1.4MHz,3MHz,5MHz,10 MHz,15MHz and 20 MHz with the standard of LTE-A.This indicates that the design in this paper meets the demands,and has lowered 50% of the complexity and achieved better performance compared with traditional FIR filters.