Abstract: We explored the influence of different concentrations of boron on the growth and physiological characteristics of Gracilaria lemaneiformis. Compared to the control, G.lemaneiformis were reddish brown and special growth rate (SGR) showed no significant difference between deficient boron group (0 mgL-1) and high boron group (40 mgL-1). The contents of Chl-a on the 6th day and allophycocyanin (APC) on the 9th day significantly decreased in the deficient boron group. The contents of phycoerythrin (PE), phycocyanin (PC) and Chl-a remarkably decreased in high boron group; while the activities of polyphenol oxidase (PPO) and catalase (CAT) significantly increased. In excess boron group (37.5 mmolL-1), G.lemaneiformis all turned green on the 6th day with negative growth of SGR; the contents of Chl-a, phycobiliprotein and soluble sugar as well as the activities of PPO and CAT dramatically decreased. Therefore, in order to ensure G.lemaneiformis production, concentration of boron in seawater must be appropriate.