Objective: Improve the brittleness and crisp of freeze-drying of pitaya. Methods: Taking red pitaya Meilong No.1 as the research object, the porosity was selected as the evaluation index by pearson correlation between sensory evaluation and objective indexes, the effects of slice thickness, pre-freezing time, drying air pressure and drying time on the quality of vacuum freeze-dried pitaya was studied by single factor experiments, and the optimal level was selected; The processing conditions were optimized using Box-Behnken response surface methodology. Results: Slice thickness, pre-freezing time and drying time were linearly correlated with the porosity of freeze-dried pitaya; The optimal process were slice thickness of 7 mm, pre-freezing time of 30 h, drying pressure of 43 Pa and drying time of 40 h, the freeze-dried pitaya produced by this process has the highest porosity, smooth surface, crisp taste and bright and uniform colour. Conclusion: The quality of freeze-drying of pitaya can be improved by using response surface methodology to optimization the slice thickness, pre-freezing time, drying pressure and drying time.