Abstract: There are provided a method named Tat-associated protein engineering (TAPE), of screening a target protein having higher solubility and excellent thermostability, in particular, an immunoglobulin variable domain (VH or VL) derived from human germ cells, by preparing a gene construct where the target protein and an antibiotic-resistant protein are linked to a Tat signal sequence, and then expressing this within E. coli, and human or engineered VH and VL domain antibodies and human or engineered VH and VL domain antibody scaffolds having solubility and excellent thermostability, which are screened by the TAPE method. There are also provided a library including random CDR sequences in the human or engineered VH or VL domain antibody scaffold screened by the TAPE method, and a preparing method thereof. There are also provided a VH or VL domain antibody having binding ability to the target protein screened by using the library, and a pharmaceutical composition including the domain antibody.