Long-term located fertilization test has been conducted to evaluate how fertilization affects the growth and yield of crops particularly rice over 30 years in the Red Soil Field Experimental Station, Chinese Academy of Agricultural Sciences, Qi Yang, China. However, how and why However, how and why fertilization influences the growth of crops in the field particularly in the paddy field has not been assessed. Consequently, an investigation was carried out in a double-rice paddy field to study the species and biomass of weeds found in rice (Oryza sativa L.) growth season after 30-year combined application of organic and chemical fertilizer with the same application rates of nitrogen (N), phosphorus (P), and potassium (K) contained in organic and chemical fertilizer in 2011. Results indicated that in both rice growth season among all fertilizer treatments, compared with other treatments, long-term application of PK+M resulted in the most species number of weeds, and the species number of weeds in early rice was 19.7% higher than that in late rice, the combined application of NPK+M showed in the fewest species number of weeds which was stable in number, and the species number of weeds in early rice was 9.8% higher than that in late rice. In the current investigation, results also demonstrated in the fewest species number of dominant weeds. Among all fertilizer treatments, the highest total biomass of weeds was founding the treatment of the combined application of NPK+M while the lowest biomass was obtained in the treatment of the combined application of NP+M in both rice growth season, subsequently, the biomass in the treatments of NPK+M, NK+M, PK+M and CK was 31.3%, 26.5%, 8.3% and 5.6% higher than the treatment of NP+M, respectively, The highest total biomass of weeds and floating weeds were found in the treatment of combined application of NPK+M while the highest total biomass of wet weeds in early rice growth season was viewed in the treatment of the combined application of NK+M, and the highest total biomass of weeds and wet weeds was found in the treatment of the combined application of NK+M, comparatively, the highest total biomass of floating weeds was obtained in the treatment of the combined application of NPK+M in late rice growth season. In the present study, soil alkali-hydrolyzable N and available P were found to be significantly positively correlated with total dry biomass of weeds, wet weeds and floating weeds (r=0.508 and r=0.578, r=0.552 and r=0.453, r=0.410 and r=0.802, the same of P < 0.05, respectively), whereas they were found negative correlation with soil pH (r=-0.516, r=-0.531 and r=-0.698, the same of P < 0.05, respectively). Soil pH was commonly affected by the soil available P, alkali-hydrolyzable N and other factors, where soil directly affects on the total dry biomass of weeds. By fertilization to maintain proper soil pH and contents of alkali-hydrolyzable N and available P, the growth of wet weeds and floating weeds in red soil paddy of south China could effectively be managed, to keep the beneficial balance between the weed species and biomass in agricultural practice.