The invention discloses a method for detecting the expression and purification of target protein by using cyanobacteria protein RbrA. The method comprises the steps of firstly, constructing a fusion gene of a target protein gene and a cyanobacterium RbrA gene or homologous genes thereof, and transferring an expression vector containing the fusion gene into an expression strain for expressing; judging whether the fusion protein is successfully expressed and/or purified or not by observing the color of supernatant and/or purified components thereof obtained after the expression strain is crushed; if the supernatant and/or the purified components thereof are in burgundy, indicating that the target protein is expressed and/or purified together with the cyanobacteria RbrA protein or the homologous protein thereof. The method can visually detect the expression and purification of the target protein, and is convenient and fast.