The invention relates to a method for efficiently cultivating lactobacillus and producing lactic acid, comprising the following steps: in the fermentation and cultivating process of lactobacillus, through adding the mixed solution of 1.0% to 50% of Na2CO3 or NaOH and 10%-50% of cane sugar or glucose, constantly controlling the pH value to be any value within the range of 5.0-8.0; and simultaneously, feeding saccharide required by the growth of lactobacillus to be served as a carbon source, thus enabling the pH to be controlled constantly and also providing a carbon-containing compound required by the growth of lactobacillus to be served as a carbon source. The invention has the advantages that in the method of the invention, the mixed solution of alkali controlling pH and carbon source saccharide feeding the growth of lactobacillus are taken as flowing liquid to control the pH value; the pH probe full-automatically and constantly controls the pH value, and simultaneous flows to supplement the carbon source required by the growth of lactobacillus, thus realizing efficient cultivating of lactobacillus and efficient production of lactic acid and having great application value in the industrial production of lactobacillus and lactic acid with high density.