Abstract: Aiming at the wide range, high integration and real-time performance on the neutron flux density measurement by International Thermonuclear Experimental Reactor (ITER) requirements, a set of multi-channel neutron flux density measurement system based on PCI extension for instrumentation (PXI) bus was designed. This system comprised a specially designed current-sensitive preamplifier and main electronics plug-in mainly including high speed analog-to-digital converter (ADC) and field programmable gate array (FPGA). The fully digital signal processing technique was utilized to join pulse counting mode and Campbelling mode, significantly increasing the neutron flux density measuring range and system integration. The neutron flux density estimation algorithm based on pulse piling-up proportion was able to choose and switch measuring modes accurately and automatically. The experiment result shows that this system achieves real-time neutron flux density measurement on a single fission chamber, and enhances upper limit of neutron radiation dose larger than 1.7×10¹⁰ cm^-2•s^-1. The entire scale relative error is below 7.1%.