The experiment designed by using table of quadratic orthogonal rotation arrays to study the effect of epidemic factors of rice sheath blight, several factors were used in our experiment:nitrogen fertlizer, phosphorus fertlizer, potash fertilizer, density and using nitrogen fertilizer periodicaly at the ear stage. The regression equation between disease index (Y) and following factor such as:nitrogen fertlizer (X₁), phosphorus fertilizer(X₂), potash fertilizer(X₃) was Y=12.37091-1.6675X₂-1.71625X₁X₃. The results showed that nitrogen fertilizer, phosphours fertilizer and potash fertilizer played a great role to the happening of Shb. Density and using fertilizer periodically at the ear stage played little role on the incidence of Shb. The results also showed that there lies interaction between different factors. We found that the interaction between nitrogen fertilizer and potash fertilizer was the greatest one.