To reduce the content of whey protein, heat-set mixed gels of potato protein and whey protein were prepared by partially replacing whey protein with potato protein at the ratio of 50/50 by weight. The physical properties of mixed protein gels at different total protein concentrations (40~80 g/L) were investigated by color, textural properties, moisture distribution and rheological properties. The results showed that the lowest gelation concentration of mixed protein gels was 50 g/L. Compared with whey protein gels formed at the lowest gelling concentration of 80 g/L, consumption of whey protein in those gels decreased by 2.20 times. When the protein concentration increased from 50 to 80 g/L, mixed protein gels exhibited yellow color in the appearance. Hardness and elasticity increased by 5.28 times and 5.90%, respectively, but the content of immobilized water decreased by 3.63%. The storage modulus G' showed weak relation with the frequency. Laser confocal microscopy and scanning electron microscopy showed that the mixed protein gels at the concentration of 80 g/L had uniform and compact gel network, small pore size, and clear spherical particle aggregation morphology, thus it had a higher G'. The results of FT-IR showed that the amount of β-folding and β-turn structures account for about 70% of the secondary structures in mixed protein gels. The results of solubility test showed that hydrogen bond and hydrophobic interaction made more contributions to maintaining the structure of mixed protein gels than disulfide bond.