The aim of this research was that using technology of simultaneous saccharification and fermentation to ferment three different carbon sources （glucose， corn starch gelatinization solution， corn starch） to produce L-lactic acid and proteomics to analysis the difference of the production under three carbon sources by Bacillus coagulans BCS13002. The results showed that the content of L-lactic acid were （10.23 ± 0.16） g/L， （11.75 ± 0.20） g/L， （0.26 ± 0.02） g/L under the carbon sources of glucose， corn starch gelatinized liquid， corn starch liquid conditions， respectively. Furthermore， 454 differential expressed proteins were identified under three different carbon sources and these were mainly involved in the glycolysis/gluconeogenesis and tricarboxylic acid cycle pathways， followed by HIF-1 signaling pathway， pyruvate metabolism， carbon metabolic， pantothenic acid and CoA biosynthesis， fructose metabolism， two-component system. Moreover， the Bacillus coagulans BCS13002 could not produce the L-lactic acid with using corn starch liquid by glycolysis/gluconeogenesis metabolism pathway. Above all the content of L-lactic acid mainly related to the difffernetial proteins in the glycolysis/gluconeogenesis and tricarboxylic acid cycle metabolism.