The invention discloses a pressure change trend-based digital non-electric quantity protection method for oil-immersed transformers. According to the method, when an oil-immersed transformer is operated, a pressure value P(t) at a measurement point of a protected oil-immersed transformer is acquired in real time, and judgement is carried out to decide whether to start a protection element or not according to the fact that whether the pressure instantaneous value P(t) at the measurement point achieves a protection starting threshold value Pst or not; if the protection element is started, a longpressure waveform of a data window with a T of 10ms is intercepted, and pressure change amounts DeltaPi at N sampling points in the data window are calculated in sequence; and statistical analysis iscarried out to obtain a number n of pressure change amounts DeltaPi which are positive values, and if n/N-1 is greater than 2/3, judgement is carried out to determine that the transformer has internal fault and the protection element acts. The method is capable of correctly distinguishing internal faults and external disturbances of oil-immersed transformers, so as to effectively avoid false action or action refuse of pressure protection elements.