Lactobacillus plantarum strain La10 was isolated and screened from kelp (Laminaria japonica) and used for the fermentation of fresh kelp. During the fermentation process, nutritional content of the fermentation products and changes in nitrite content were determined. The results showed that the optimal conditions were as follows: (1) The OC1 fermentation conditions for sensory evaluation as the ultimate target were: temperature 20 ℃, amount of inoculum 5%, sugar concentration 9%, salt concentration 4%, and duration of fermentation 10 d. (2) The OC2 fermentation conditions for total acid in the fermentation liquid as the ultimate target were: temperature 30 ℃, amount of inoculum 10%, sugar concentration 9%, salt concentration 2%, and duration of fermentation 7 d. (3) The fishy smell in the kelp fermentation products was eliminated. Using OC1 and OC2, algin content decreased significantly from 32.07% to 19.60% and 14.01%, respectively. In contrast, reducing sugar and total sugar content increased significantly from 2.19% to 9.15% and 11.01%, respectively. The taste of the kelp fermentation products was better than that of non-fermented products. During the fermentation, nitrite content remained at a low level and the final values, using the two kinds of fermentation conditions were 93.99 and 71.43 μg/kg, respectively, which were far lower than that of the national standards used (20 mg/kg in pickles).