Fishery resources density, spatial distribution, and size composition were studied in February, April, September, and November 2017, primarily based on an acoustic method to explore the fish gathering effect of artificial reefs in Fangchenggang Gulf. A total of 201 nekton and benthic invertebrate species (including 126 fish species, 32 crab species, 20 decapod species, 11 squilloidea species, and 12 cephalopoda species) were collected in artificial reefs (and areas adjacent to the reefs) in the Fangchenggang Gulf. The results of a two-way ANOVA showed that the spatial and temporal differences in fishery resource density in the investigated area are significant (<0.001). The interaction between seasons and regions is also significant (<0.001). The fishery resource density of the artificial reefs area (547745 ind/n mile²) was nearly 2.7-times greater than that of the surrounding area (203990 ind/n mile²), showing an obvious fish gathering effect of artificial reefs in February. The types of fish were mainly benthic and rockfishes such as . Small size individuals accounted for a large percentage in the artificial reef area and their average target strengths (TS) were -55.6 dB (in February), -54.5 dB (in April), -53.6 dB (in September), and -52.2 dB (in December), respectively, which displayed a gradually increasing trend of TS values with the individual growth. In the vertical direction, more than 90% of single echo detections were distributed in the middle and deeper layers (9~16 m) of the artificial reef area in the February and April investigations. In conclusion, the construction of artificial reefs in Fangchenggang Gulf revealed an obvious downward gathering effect on the small size rockfishes, which supports the need for systematic evaluation of the ecological effect of marine ranching.