The fission chamber plays a key role in International Thermonuclear Experimental Reactor (ITER) neutron flux measurement. However, the matched preamplifier cannot tolerate the strong radiation of ITER. This can be solved by using a cable to transmit the signal from the detector to the preamplifier. The object of this project is to develop charge preamplifiers that admit a long cable as input. The input stage and gain stage of the charge preamplifier in previous work have been improved to reduce the rise time and noise degradation caused by the capacitance of the long cable. The experimental results confirm that the preamplifier can admit the fission chamber detector and a 20-m cable.