Bitter melons are rich in active substances, such as saponins, polysaccharides, peptides andflavonoids, which have a high edible and medicinal value. Drying the bitter melons can extend the shelf life. There are some commonly drying techniques, such as sun drying, hot air drying, microwave drying and spray drying. But the active substances are easily to be damaged during the drying process due to high temperatures. Vacuum freeze-drying technology completely freezes the material and then heats it in a vacuum to sublimate the water in the material. So it can be as much as possible to retain the material’s color, shape, nutritional composition and the products have a good quality.In order to improve the quality of dried bitter melon, the vacuum freeze-drying technology was used to dry the bitter melon slices to get the best process parameters in this paper. Because the eutectic temperature referred to the temperature which could make the material completely frozen during the freezing process, the eutectic temperature of fresh bitter melon was first measured.The eutectic point temperature of bitter melon was -19℃. It was determined that the pre-freezing temperature of bitter melon was -30℃ and the pre-freezing time was set to 2h. On the basis of single factor test, the quadratic polynomial regression model between inspection indexes (moisture content, rehydration ratio) and drying parameters (slice thickness, temperature, working pressure, drying time) of the bitter melon slices were established by response surface methodology (RSM).Under the condition that the moisture content is less than the safe water content (10%), the optimum process parameters are obtained by optimizing the rehydration ratio using the genetic algorithm in Matlab. The results showed that the regression equation had a good fitting degree (R2=0.9371,R2=0.8548), the model was significant and the obtained process parameters were reasonable.The thickness, pressure and drying time had significant effect on the moisture content during the drying process. They also had significant effect on the rehydration ratio. The interaction between the partition temperature and the pressure had significant effect on the two indexes. The results were optimized by genetic algorithm. After being verified, the optimum technological parameters were slice thickness of 4mm, heating plate temperature of 46℃, absolute pressure of 73Pa and drying time of 8.7h. In this condition the moisture content was 6.23% and the rehydration ratio was 11.75. The study provides reference for vacuum freeze drying bitter melon slices and other materials.