[Background] Alginate oligosaccharides produced by enzymatic hydrolysis of alginate have diverse biological functions such as anti-oxidation, anti-tumor, induction of immune regulation, and regulation of plant growth, and exhibit broad application prospects in the fields of food and medicine. Mass screening of alginate-degrading bacteria is beneficial to obtain new structures and functions of alginate oligosaccharides, which is conducive to actively promoting the industrial progress of oligosaccharides. [Objective] High-efficiency screening was carried out for alginate-degrading strains and exploring the in situ microbial resources of seaweeds with development prospects. [Methods] The only carbon source of sodium alginate was used to select the microorganisms on the surface of brown seaweed. The chromogenic reaction of gram iodine solution indicated the characteristics of microorganisms to degrade alginate. The activity of alginate lyase was determined by Oxford cup method. [Results] A total of 81 colonies were obtained from the surface of the algae samples. Twenty-eight strains were screened by clear circle staining. Seven strains of alginate-degrading bacteria were identified by 16S rRNA gene sequencing analysis. They belonged to the genus Bacillus (3/7), Arthrobacter (1/7), Desemzia (1/7), Brachybacterium (1/7) and Streptosporangium (1/7). The genera Arthrobacter, Desemzia, Brachybacterium and Streptosporangium have not been previously reported to produce alginate lyase. Further analysis showed that T-1 strain (Bacillus) had maximum enzyme production and highest enzyme activity. [Conclusion] Seven alginate lyase-excreting strains were isolated, and the enzyme activities of the strains were compared by Gram’s iodine coloration combined with the Oxford cup method. This indicates that the screening method is simple, efficient and suitable for large-scale screening of alginate lyase-excreting microorganisms.