Abstract: To improve the accuracy of fisheries resource assessment in marine ranching, we conducted an acoustic survey in the marine ranching demonstration area that is in the southern sea area of Yintan, Guangxi in January 2023, by using two advanced split-beam echo sounders: the EK80 (Operating frequency: 120 kHz) and the EY60 (Operating frequency: 200 kHz), with the biological sampling through bottom trawling. According to the comparison between frequency-difference noise-reduction techniques and traditional noise-reduction methods in the analysis of fisheries acoustic data, compared with traditional techniques, the frequency-difference noise reduction yielded a higher average target strength (TS) with a smaller variation range when tracking single targets, demonstrating greater technical precision and objectivity. When assessing the fish density across different transects, we found that the average count density obtained through frequency-difference noise reduction was consistently lower than that derived from traditional methods, showing its reliability in handling acoustic noise in fisheries assessment. For dominant species, the frequency-difference noise reduction showed insignificant differences in the count density for larger individuals, but a significant increase for smaller individuals, highlighting its advantage in enhancing assessment accuracy for fish density. Therefore, using volume backscattering strength (Sv) images processed with frequency-difference noise reduction for fisheries resource density assessment can more effectively eliminate interfering noise and accurately detect smaller biological targets, ultimately improving the precision of fisheries resource assessment in marine ranching.