Abstract: To test remediation effects of balanced fertilization on a paddy soil with long-term K-deficiency, a pot experiment has been being carried out since April, 2005 with five fertilization treatments (NPK, NPKSi, NPKOM, NPhK and NPhKOM）. The results showed that the amount of bacterium and actinomyces, microbial biomass C and the microbial activities increased, and the rate of mineralization of organic nitrogen and phosphorus promoted with the increasing application rate of silicon fertilizer (NPKSi) or potassium fertilizer (NPhK). While the above mentioned parameter appeared an opposite trend with the addition of organic manure (NPKOM) because it resulted in a worse anaerobic condition though the microbial biomass N and P increased. Increasing potassium application companied with organic manure (NPhKOM) increased microbial biomass C and microbial activity, but decreased the amounts of microbe. Consequently, applying silicon or potassium fertilizer may remediate the paddy soil with long-term K-deficiency more efficiently. Excessive application of organic manure application should be avoided. Combine application of silicon fertilizer or potassium fertilizer was recommended suppose large amount of organic manure was addressed under our study condition.