To investigate the effect of in the “rice-duck-crayfish” model(CDR) on soil fertility in paddy fields, the physical, chemical and biological properties of the soils were compared between CDR and the rice monoculture model(RM) by using field experiments and sampling tests and analysis after rice harvesting in 2022-2023. The soil fertility of the two models was comprehensively evaluated by combining the fuzzy comprehensive evaluation method and the simple linear scoring method. The results showed that soil microbial biomass nitrogen significantly decreased by 53.27% after 2 years of CDR; the soil organic matter, total nitrogen, available potassium and microbial biomass carbon showed an increasing trend, and the soil pH, available nitrogen, available phosphorus, acid phosphatase and alkaline phosphatase declined, but none of them showed a significant difference. Compared with RM, except for the microbial biomass nitrogen, other indicators showed different degrees of reduction. From the perspective of soil fertility, there was no significant difference between CDR and RM under 2-year planting and rearing conditions, but the soil fertility index of the paddy field in CDR showed an increasing trend, with an increase of 7.94%, while the soil fertility index decreased in RM, and the soil fertility index of CDR was 3.03% higher than that of RM in 2023. Therefore, there was no significant change in the soil fertility of paddy fields under CDR in two years.