Alginate lyase as the excellent tool enzyme could produce alginate oligosaccharides under mild reaction conditions and good specificity. Herein, the new Ca2+ activated alginate lyase gene (TAPL7B) with metal ions stability and cold-adapted was cloned and expressed heterologously from Thalassotalea algicola. TAPL7B was identified as a polysaccharide lyases family 7 (PL7) alginate lyase with endolytic activity. TAPL7B is a polyM-preferred and cold-adapted enzyme with an optimal temperature of 20 °C and pH 11.0. The pH stability analysis indicated that TAPL7B possessed broad pH tolerant range (4.0–12.0) and preferred alkaline environments. Interestingly, the enzymatic activity of TAPL7B was greatly activated by Ca2+ and it increased 9-fold in the presence of 1.2 mM Ca2+, which is rare in other alginate lyases. The activity of TAPL7B is not only activated by Ca2+, but also by some other metal ions (such as K+, Na+, Ni+, Cu2+, Mg2+, Zn2+, Co2+, Fe3+). The results of fast protein liquid chromatography (FPLC) and electrospray ionization mass spectrometry (ESI-MS) indicate that TAPL7B adopts an endo-action mode on all three substrates, and the products are all oligosaccharides with a degree of polymerization of 2–6. Therefore, the cold adaptability, broad pH stability, excellent metal ions stability, and Ca2+ activation of TAPL7B make it a potential industrial biocatalyst for the preparation of alginate oligosaccharides.