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As for freezing injury prevention in greenhouse vegetables， the temperature adjusting method by building sheds and covering multi layer plastic films is used widely. Temperature observation of microclimate environment in greenhouse with this multi layer plastic film covers was conducted, and temperature correlativity inside and outside the greenhouse is analyzed. The unary linear regression forecast models of daily minimum temperature in greenhouse are built, and daily minimum temperature in greenhouse is predicted by using the models and the daily minimum temperature of weather forecasts. The number of plastic film covers was determined on the basis of the forecast results and vegetable freezing injury indexes, and the countermeasure with the plastic film cover method is proposed to prevent freezing injury for greenhouse vegetables, which give references for the safe production of facility agriculture.