The work aims to establish the shelf life model of fresh milk to study the change rules of fresh milk quality parameters. The changes of fat, protein, pH and acidity of fresh milk under conditions of different storage time and temperature were analyzed. The kinetic characteristics of fresh milk quality parameters were studied by food chemical reaction kinetics equation and Arrhenius equation. The fat, protein and pH values of fresh milk showed a decreasing trend during storage, while the acidity showed an increasing trend. 4 °C could slow down the decline of pH value and the rise of acidity of fresh milk. Acidity can express the quality change process of fresh milk well, and the activation energy of fresh milk acidity and the shelf life model of fresh milk based on acidity are obtained by studying the kinetic characteristics of chemical reaction.