Abstract: Correlation analysis of fermentation parameters has been effectively applied to process optimization of several fermentation products.The composition of exhaust gas,consumption of carbon and(nitrogen) sources,concentration of product formed during the inosine production of Bacillus subalis were analyzed and calculated.The whole process was classified into four phases according to the state parametes on engineering scale,i.e.the correlation of oxygen uptake rate(OUR), carbon dioxide evolution rate(CER),respiratory quotient(RQ) and product yield to glucose(Y_(P/G)).It gives a clue to the researches on other scales and fermentation process optimization.