The invention relates to blue active dye with high alkali resistance and a preparation method of blue active dye. The active dye has a general structural formula (I): (shown in the description). The blue active dye prepared by the method is not only high in color fixation rate, alkali resistance and light fastness, but also high in solubility, has the most obvious advantage of alkali resistance, and can meet the cold-pad-batch strong-basicity requirement. The blue active dye is suitable for dyeing cotton, hemp and wool fibers and has good performance.