Experiments were carried out in Hongze county, Jiangsu province, for pistia stratiotes shoot protection in the cold months of 1972-1978, Based on the experimental data some mieroclimatic characteristics of hotbeds are examined in this paper. Short wave radiation balances of both hotbeds with plastic filmy cover and those with glass cover are compared. Calculation methods and thus the results are produced for the determination of the heat generative power and temperature conductivity coefficients of thermofermentable substances and of the heat flow therein. The rest of the components in the heat balance equation of hotbed are also discussed. Suggestions are then made as to the structure of the hotbeds as well as the management for the postia stratiotes shoot protection.