Based on analyzing the water retention curves in paddy soils of long-term fertilization, the relationship between soil properties and different pore size were explored. The results showed that soil organic carbon content and water-holding capacity increased with the application of organic manure. Compared to the no fertilizer treatment (aeration porosity 0.121 m3/m3), the organic manure application treatment increased aeration porosity (aeration porosity 0.156 m3/m3), whereas the chemical fertilizer application treatments decreased aeration porosity (NK 0.11 m3/m3, NP 0.115 m3/m3, NPK 0.082 m3/m3, 2NPK 0.113 m3/m3). The proportion of marcopores and mescopores were 1.45-1.68 and 1.22-1.43 times for organic manure application treatment to the no fertilizer treatment and the chemical fertilizer application treatments, the proportion of mircopores in 0.39 - 0.41 m3/ m3. Correlation analysis showed that the content of soil organic carbon exhibited significant correlates with total porosity and the proportion of mescopores (P<0.01) and significant correlates with the proportion of marcopores (P<0.05), but not significant with the proportion of mircopores; the proportion of macropores had significant correlates (P<0.05) with soil microbial biomass carbon and respiration intensity. These results suggested that long-term application of organic manure could improve the total porosity via the increase of the mescopores and marcopores, and the increased soil macropores could favor soil microbial activities.