Because of its high photo-thermal conversion efficiency, the parabolic trough solar collecting system in solar thermal power generation is more mature. Therefore，in recent years more and more applications were made in the field of forage drying. In order to further improve the efficiency of forage drying, as steady output of dry hot wind energy，the parabolic trough solar collecting system, the heat collecting performance and heat loss of vacuum heat collecting pipes were studied. Through studying，the factors that improved the heat gathering efficiency of the system was found out. Tracking the inlet, outlet and inner temperatures of a vacuum heat collector by heating the heat transfer oil storage energy using a slot solar heat collector system. The effect of instantaneous temperature of heat transfer oil was discussed from different angles, especially when entering vacuum heat collector on the transient heat conversion efficiency of heat collector. It can be deduced from the opposite side that the instantaneous heat conversion efficiency of the collector was related to the temperature of the heat guide medium when entering the collector. The lower the temperature of the heat transfer oil of the collector was, the more full the heat exchange was, and the less the heat loss of the vacuum heat collector can be got, the higher the instantaneous heat conversion efficiency of the collector can be obtained. So how to increase the heat transfer oil temperature difference between the outlet and inlet of the collector was the key to improve the heat storage capacity.