It is needed to achieve very high multipath delay accuracy in order to better approximate the real communication scenario in the process of channel simulation, which puts higher requirements on the simulation ability of the channel emulator. Channel models is processed and loaded usually within the digital baseband, and so the clock resolution is limited.It is necessary to make use of Farrow structured fractional filters to achieve higher delay accuracy . In according to the characteristics of channel simulation algorithms， the Farrow structure fractional filter was designed and optimized by mixing DSP and distributed multiplication to achieve ultra high precision delay simulation. The design scheme was validated and tested on the TRANSCOM Pathrot X80 channel emulator. The results show that: 1) the improved Farrow filter's structural design significantly reduces the consumption of FPGA computing resources, enabling the fractional delay algorithm to achieve a balance between high delay accuracy and low resource overhead; 2) the multipath delay accuracy is consistent with theoretical calculations in the low frequency range, meeting the expected 0.1ns requirement for channel simulation; 3) the delay accuracy differs significantly from theoretical calculations in the high-frequency range. In order to achieve better performance or reduce signal distortion, it can be considered to increase the order of the filter or find a better coefficient calculation algorithm.