The present invention relates to an oil collection tank having an expansion ring, and an application thereof. The oil collection tank comprises a liquid collection cap, a liquid collection groove, a liquid collection groove position limitation device, a tower ring, a filler plate, a position limitation expansion ring, a bracket, a liquid collection channel, a pulling-out hopper and a support rib plate. One end of the liquid collection groove is fixed on the liquid collection channel, and the other end is fixed on the filler plate. The liquid collection groove position limitation device is arranged on the lower part of the filler plate connected to one end of the liquid collection groove. The lower part of the other end of the filler plate is overlapped on the tower ring. The upper part of the filler plate is connected with the position limitation expansion ring. The oil collection tank of the present invention has the following advantages that: excellent functions of gas distribution and liquid collection are provided, staying time of the collected liquid can be reduced, occurrence of coking can be prevented, the oil collection tank can freely expand at a high temperature without limitation of operating temperature, and normal operation of the tower under the high temperature operating condition is ensured.