A preparation method of porcine reproductive and respiratory syndrome vaccines by utilizing a bioreactor utilizes a stream perfusion type bioreactor as a cultivation tool. The preparation method comprises the steps of a cultivating cells for preparing the vaccines; b vaccinating and cultivating viruses; c harvesting virus liquor; d preparing the vaccines and the like. The preparation method has the advantages that the preparation method is simple and convenient in operation, low in contamination probability and capable of remarkably reducing preparation cost, the vaccines are large in yield, uniform and stable in quality and good in immune effect, and the like. The whole preparation process does not involve other problems of biological safety and public hygiene so that the preparation method is suitable for large-scale preparation of the porcine reproductive and respiratory syndrome vaccines.