A method for achieving the regulated expression of two proteins, comprising the following steps: said two proteins are named as protein A and protein B, respectively; protein A-encoding gene is located in an expression cassette A-I, and protein B-encoding gene is located in an expression cassette B-I; said expression cassette A-I comprises the following elements successively from upstream to downstream: a feedback element coding sequence, a promoter A, a protein A-encoding gene and TALER protein A-encoding gene linked by means of self-cleaving polypeptide encoding gene, a target sequence A-I; said target sequence A-I comprises more than one shRNA1 target sequence; said expression cassette B-I comprises the following elements successively from upstream to downstream: a feedback element coding sequence, a promoter B, a protein B-encoding gene and TALER protein B-encoding gene linked by means of self-cleaving polypeptide encoding gene, a target sequence B-I; said target sequence B-I comprises more than one shRNA2 target sequence; in said expression cassette A-I, both the upstream and downstream of said promoter A have at least one said TALER protein B target, respectively, or the upstream of said promoter A has no said TALER protein B target but the downstream thereof has at least one said TALER protein B target; in said expression cassette B-I, both the upstream and downstream of said promoter B have at least one said TALER protein A target, respectively, or the upstream of said promoter B has no said TALER protein A target but the downstream of said promoter B has at least one said TALER protein A target; an expression cassette C is obtained, said expression cassette C comprises a constitutive promoter- and an activating element-coding sequence successively from upstream to downstream; a DNA positioned downstream of said feedback element coding sequence is expressed under the stimulation of said activating element; a recombinant vector A-I with said expression cassette A-I, a recombinant vector B-I with said expression cassette B-I, and a recombinant vector C with said expression cassette C are introduced into host cells, and the expression of said protein A and the expression of said protein B are regulated by adding shRNA1 or shRNA2. characterized in that: in said expression cassette A-I, the upstream of said promoter A has one said TALER protein B target and the downstream of said promoter A has one to three said TALER protein B targets; in said expression cassette B-I, the upstream of said promoter B has one said TALER protein A target and the downstream of said promoter B has one to three said TALER protein A targets. said two proteins are named as protein A and protein B, respectively; protein A-encoding gene is located in an expression cassette A-I, and protein B-encoding gene is located in an expression cassette B-I; said expression cassette A-I comprises the following elements successively from upstream to downstream: a feedback element coding sequence, a promoter A, a protein A-encoding gene and TALER protein A-encoding gene linked by means of self-cleaving polypeptide encoding gene, a target sequence A-I; said target sequence A-I comprises more than one shRNA1 target sequence; said expression cassette B-I comprises the following elements successively from upstream to downstream: a feedback element coding sequence, a promoter B, a protein B-encoding gene and TALER protein B-encoding gene linked by means of self-cleaving polypeptide encoding gene, a target sequence B-I; said target sequence B-I comprises more than one shRNA2 target sequence; in said expression cassette A-I, both the upstream and downstream of said promoter A have at least one said TALER protein B target, respectively, or the upstream of said promoter A has no said TALER protein B target but the downstream thereof has at least one said TALER protein B target; in said expression cassette B-I, both the upstream and downstream of said promoter B have at least one said TALER protein A target, respectively, or the upstream of said promoter B has no said TALER protein A target but the downstream of said promoter B has at least one said TALER protein A target; an expression cassette C is obtained, said expression cassette C comprises a constitutive promoter- and an activating element-coding sequence successively from upstream to downstream; a DNA positioned downstream of said feedback element coding sequence is expressed under the stimulation of said activating element; a recombinant vector A-I with said expression cassette A-I, a recombinant vector B-I with said expression cassette B-I, and a recombinant vector C with said expression cassette C are introduced into host cells, and the expression of said protein A and the expression of said protein B are regulated by adding shRNA1 or shRNA2. characterized in that: in said expression cassette A-I, the upstream of said promoter A has one said TALER protein B target and the downstream of said promoter A has one to three said TALER protein B targets; in said expression cassette B-I, the upstream of said promoter B has one said TALER protein A target and the downstream of said promoter B has one to three said TALER protein A targets.