A digital protection device for a transformer based on single pressure information and a method. The device comprises a transient oil pressure characteristic quantity measuring module, a digital inputmodule, a signal conditioning and acquiring module and a digital core module. The transient oil pressure characteristic quantity measuring module is connected with the signal conditioning and acquiring module, and both the signal conditioning and acquiring module and the digital input module are connected with the digital core module. The invention acquires the transient oil pressure digital information at a plurality of measuring points in an oil tank in real time and calculates a single operating pressure value characterizing the oil pressure magnitude; a protection criterion and a threshold value setting method are constructed according to the significant difference of the characteristic quantity under different operation conditions of the transformer, thereby reliable, rapid and sensitive identification and removal of fault in the transformer tank are realized. The invention is not affected by magnetizing inrush current, and is suitable for the "four characteristics" requirementsof the existing and future high-capacity high-voltage class power transformers on non-electric quantity protection.