In order to investigate the effect of calcium on low methoxyl pectin/sodium alginate mixed gel system, different concentration of CaCl2 was added into 1 g/100mL of mixed gel system to study the changes in rheological properties and microstructure. The results showed that the shear stress of the mixed gel system decreased with the addition of Ca2+ and reached its minimum at 9 μmol/mL, but shear stress increased after continuing adding Ca2+. The viscosity of the mixed gel system increased with Ca2+, and the mixed gel exhibited the characteristics of the typical pseudoplastic fluid. After adding Ca2+, the fluid index n of the mixed gel system decreased, and the consistency coefficient K was at the highest at the concentration of 9 μmol/mL. The dynamic viscoelasticity of the composite gel changed obviously with the increasing of Ca2+. The storage modulus of the gel system increased with the addition of Ca2+, but the loss tangent decreased gradually. The loss tangent rose again when the calcium ion concentration was more than 9 μmol/mL. Microstructure observation showed that Ca2+ contributeed to the formation of gel pores and when the amount of Ca2+ was at 9 μmol/mL, the mixed gel system had the largest and most dense pores. The number of pores in the gel decreased and the gel network was no longer strong after continuing adding Ca2+, at which point, the scanning electron microscopy was more similar to the mixed gel system without Ca2+.