Abstract: The physiological maturity and growth period of edible mushrooms are conventionally measured and described qualitatively. To find a quantifiable measurement for them, a nutrition unit was firstly defined to be the daily growth of mycelia in length. Secondly, based on the nutrition unit, a theoretical model for the fungal development was established. Thirdly, using a dominant nutrition unit that governed the degree of maturity of a mushroom, a mathematic model was constructed. Finally, 2 strains of mushrooms, Pleurotus cornucopiae and Pleurotus citrinipileatus, were subjected to a planting experiment to evaluate the parameters in the prediction model. The experimental data on the cultivation successfully fitted the function as it predicted. It was, Pleurotus cornucopiae , and Pleurotus citrinipileatus , thus, concluded that a quantified protocol to describe and predict the physiological maturity and for the determination of cultivation duration of a mushroom was established, f(x, L)=.