The invention discloses a genetic therapy breast cancer drug preparation method based on microfluidic chip, which includes that: the method adopts biological molecules as computation medium to compute the cancer-related gene expression through biochemical reaction; when the result meets the requirement, the anti-cancer drug is automatically synthesized and released in targeted manner; the anti-cancer drug is complete suicide gene; the biological molecules used as computation medium are DNA molecules and / or enzyme; the oncogene related to breast cancer includes: C-erbB-2, EGFR, c-myc, ras, int-2, bcl-2, BAG-1, BCSG-2 and survivin; the cancer suppressor gene related to breast cancer includes P53, nm23, PTEN, Rb, P16, P21, CHEK2, BRCA1 and BRCA2. The invention can synthesize and release anti-cancer drugs for breast cancer on specified conditions; and the anti-cancer drugs are complete suicide gene. The method can be combined with the nanometer technology and micromachining technology to help improve the treatment effect.