The invention relates to the technical field of transformer excitation inrush current suppression in power systems, in particular to a transformer excitation inrush current suppression device and suppression method based on residual magnetism estimation. Based on the estimation of residual magnetism of a transformer, no-load switching is carried out on the transformer by controlling the closing time of a circuit breaker, and thus, excitation inrush current is suppressed. Excitation inrush current suppression is realized by the transformer excitation inrush current suppression device as well asthe original voltage and current transformers and transformer outlet circuit breaker of a power system. The transformer excitation inrush current suppression device includes a CPU processing module board, an AT board (namely, TA/TV module), an MOSFET module board, a power module board and a bus board. The residual magnetism in the iron core can be estimated accurately. The optimal closing time can be calculated. A closing signal can be sent to the circuit breaker according to the mechanical characteristics of the circuit breaker. The excitation inrush current at the no-load closing time of the transformer can be reduced. The impact of the excitation inrush current to the transformer can be reduced. The transformer differential protection action can be avoided. Harmonics caused by no-loadclosing can be reduced. The influence of the power transmission of surrounding DC converter stations can be avoided.