Rhodospirillum rubrum (R. rubrum) water treatment technology could recycle bio-resource. However, the inability to degrade macromolecular organics limited its wide application. This paper discussed the feasibility of small molecular carbon source promoting R. rubrum directly treatment dairy machining wastewater (DMW) and accumulations for single cell protein and pigment, and establishment of mathematical model. Six small molecules promoted the degradation of macromolecules (proteins) in DMW. They promoted protease secretion and non growth matrix (protein) decomposition in DMW through co metabolism. Among, 550 mg/L potassium sodium tartrate was the best, protease activity and protein removal rate were increased by 100% comparing with control. Then, chemical oxygen demand (COD) and protein removal rates reached 80%, the single cell protein, carotenoid and bacterial chlorophyll yields were increased 2 times. Meanwhile, carbon nitrogen ratio (C/N), food microbial ratio (F/M) were identified as the most important factor by principal component analysis. Multivariate nonlinear equation model between COD removal rate and C/N, F/M, time was established.