The invention discloses an ultrahigh permeability bread yeast and a preparation method thereof, and relates to a pattern biological bread yeast, which can be used for detecting environmental genotoxic carcinogen. Through reconstruction of genetic gene technology, the yeast has improved permeability, so that the yeast has wider detection range and higher sensitivity to environmental pollutants. Through gene knock-out technology, genes CWP1 and CWP2, which are used for encoding protein mannose protein serving as an important structure of bread yeast cell wall, is inactivated to improve the permeability of the bread yeast cell wall to environmental carcinogen; and genes SNQ2 and PDR5, which are used for encoding an efflux pump protein on a cell membrane of bread yeast, is inactivated to improve the accumulation of the environmental pollutants in the bread yeast cell. Through the integration of two reconstruction strategies, an RNR3-1acZ system is constructed when four genes CWP1, CWP2, SNQ2 and PDR5 knock out bread microzyme, which can improve the sensitivity of the system to detecting the environmental genotoxic carcinogen.