The invention disclose a manufacturing method of stainable alginate fibers, which comprises the following steps of: adding a water-soluble dendrimers compound into a alginate fiber spinning solution, and solidifying, drafting, water washing and post-processing by adopting wet spinning equipment and technology to obtain the alginate fibers with excellent staining property, wherein the content of dendrimers in the alginate fibers is 1-10 percent. Compared with a traditional alginate fiber production technology, the invention has the advantages that the prepared alginate fibers can be applied todirect dyes and active dyes under a salt-free condition to realize staining and have higher dye uptake rate which generally reaches above 80 percent and is 10-15 times that of the alginate fibers produced by the traditional technology. In addition, the alginate fibers prepared by the invention has better color fastness and particularly excellent wet-processing fastness which reaches above grade 4.