The invention discloses an oil seal structure and an oil seal method for a cooling 
transformer, comprising an upper cover plate, the upper cover plate is arranged in the inner cavity of an 
oil tank of a 
transformer, and the long side of the upper cover plate is connected with a 
long axis side oil seal  One end of the 
cardboard, the other end of the oil seal 
cardboard on the 
long axis side is in contact with the bottom inner wall of the 
fuel tank, one end of the oil seal 
cardboard on the 
short axis side is connected to the broad side of the upper cover plate, and the other end of the oil seal cardboard on the 
short axis side  One end is in contact with the bottom inner wall of the 
oil tank, the oil seal cardboard on the 
long axis side, the oil seal cardboard on the 
short axis side, the upper cover plate and the inner wall at the bottom of the 
oil tank of the 
transformer enclose the cavity of the 
synthetic oil seal structure, the other end of the oil seal cardboard on the long axis side and  The other end of the oil seal cardboard on the side of the short axis is bent toward the cavity inner cavity of the oil seal structure, and the upper cover plate and the inner wall of the bottom of the oil tank are connected by a support member.  The invention has low manufacturing cost, and the cavity of the oil seal structure has 
scalability, which ensures a stable flow rate of oil entering the coil.