The invention relates to a TCR soft start and SVC dynamic reactive power compensation device and a soft start and dynamic reactive power compensation method. The device comprises a TCR branch circuit, an FC branch circuit, a start switching loop, an operation switching loop and a control system; the TCR branch circuit comprises a first phase control electric reactor unit, a thyristor valve group unit, a second phase control electric reactor unit, a first switch and a second switch; the TCR branch circuit, the start switching loop and a motor are connected in sequence and connected with a power gird system bus, and a parallel bypass of the operation switching loop is connected between the power grid system bus and the start switching loop; and the thyristor valve group unit is a soft start device of the motor during motor starting, and the TCR branch circuit and the FC branch circuit are used as dynamic reactive compensation devices during operating or stopping of the motor. The TCR soft start and SVC dynamic reactive power compensation device and the soft start and dynamic reactive power compensation method are suitable for both the soft start of a high voltage motor and the reactive power compensation adjusting on the power grid, have multiple functions, and meanwhile have the advantages of simple structure, convenience for operation and maintaining, good performance, stability and reliability, and the equipment investment is reduced.