We analyzed the main problems that exist in the writing process of the scientific English for non-English major postgraduates in natural science fields, established a training mode for improving the English writing ability of non-English major postgraduates, and elaborated three main links in training mode in detail, including the accumulation of professional vocabularies and sentence patterns, the cognition of structure and expression of the scientific English paper, and the conciseness of research contents. The practical results indicate that the training mode is feasible and very fruitful for the development of talent training mechanism of modern university system and improvement of the scientific English writing ability, and can be applied in the training of writing ability for non-English major postgraduates.