Objective To establish a transgenic humanized ACE2 nude mouse model against a BALB/ c-nude mouse background. Methods Female human ACE2 (hACE2) transgenic mice were hybridized with male BALB/ c-nude mice to produce an F1 generation. An F2 generation was then obtained by backcrossing the F1 generation hACE2 mice with BALB/ c-nude mice, and F3 generation hACE2 transgenic nude mice were obtained by intercrossing the F2 generation hACE2 mice. Finally, F3 hACE2 transgenic nude mice were compared with C57BL/ 6J wild-type mice, hACE2 mice, and BALB/ c-nude mice in terms of their phenotypes, and physiological and immunological characteristics. Results (1)There were no significant differences between hACE2 transgenic nude mice and C57BL/ 6J wild-type mice, hACE2 mice, or BALB/ c-nude mice in terms of their phenotypes. (2) hACE2 transgenic nude mice had similar physiological indexes to BALB/ c-nude mice and lacked thymuses. However, the spleen and liver indexes differed significantly between hACE2 transgenic nude mice and BALB/ c-nude mice ( P< 0.05). Routine blood indexes also showed that the neutrophil, lymphocyte, and monocyte percentages differed significantly between hACE2 transgenic nude mice and C57BL/ 6J wild-type mice and hACE2 mice (P < 0. 01). (3)There were also significant differences in immunological indexes between hACE2 transgenic nude mice and C57BL/ 6J wild-type mice and hACE2 mice in terms of the percentages of CD3, CD4, CD11B, and natural killer cells (P< 0.01), but no significant differences between hACE2 transgenic nude mice and BALB/ c-nude mice. Conclusions We successfully established a line of hACE2 transgenic nude mice with a BALB/ c-nude mouse background.