Background. Pleurotus sajor-caju has nutritional and medicinal values but it cannot be stored for more than 24 hours at room temperature because of its high water content. In addition, using the Modified Atmosphere in Packaging (MAP) method to store fresh mushrooms is an effective way to extend their shelf life. Materials and methods. The protein, total sugar and lipid contents were determined for fresh oyster mushrooms packed in paper (P), high-density polyethylene (HDPE) and polyethylene terephthalate (PET) at 3–5°C and 28–30°C (with 60–62% and 76–78% of air humidy, respectively) during storage. The kinetics of chemical degradation were explored, and the best model was selected based on the highest R2 value and the lowest RMSE value. Results. The loss of protein, total sugar and total lipid contents were lowest in the samples packed in HDPE packaging. Changes in the kinetics of protein and total sugar in different packaging and temperatures during storage followed the first-order model, while changes in total lipid followed the zero-order model. The halflife (t 1/2) values of the samples at 3–5°C were 4–5 times higher than at 28–30°C. Conclusion. The use of HDPE packaging was effective in maintaining the composition of Pleurotus sajor- -caju at 28–30°C for 2–3 days and 13–15 days at 3–5°C.