Solar-thermal technology was widely applicated in the field of alfalfa drying already, Solar low temperature drying technology can minimize the loss of alfalfa nutrient compositions. The aim was to improve solar drying efficiency and optimize the drying process parameters of 9TGK-1.5 solar grass drying unit equipment. Firstly, the factors influencing the drying of alfalfa was studied. The experiment and analysis of the low temperature drying process of alfalfa were studied through drying test bed. The changing rules of drying temperatures, wind speeds, drying rates, drying base moistures and drying times were found out. The conclusion was obtained that in the first stage of drying process, the temperature can be chosen as 50℃, wind speed can be 1.5m/s in order to save energy. When drying process in the second and third stages, in order to achieve the effect of rapid drying, the temperature can be chosen as 50℃, wind speed can be 2.5m/s. Experiment results showed that the Page equation was consistent with the drying process of alfalfa. The fitting regression of drying model of alfalfa was completed. The optimized parameters were adopted to improve the efficiency of alfalfa by 34.4%. It can improve the effective control of aromatic amino acid volatilization and protein denaturation, and increase the content of crude protein and carotene in alfalfa hay. The research result provided an optimized basis for the design of the related parameters of solar drying technology and drying equipment.