The utility model belongs to the technical field of automatic control of a power system, and particularly relates to a scattered power generation reactive compensation device and a method with the harmonic suppression function. The scattered power generation reactive compensation device comprises an A-T mixing reactive compensation unit, a central control unit and a power supply module. The A-T mixing reactive compensation unit comprises a thyristor control reactor set (TCR), an active power filter (APF) and a passive filter set, wherein the thyristor control reactor set is connected with a compensation access point between the passive filter set and a power grid main line, and the active power filter and the passive filter set are in serial connection to form a mixing active filter. The central control unit can output pulse width modulation signals and triggering pulse signals which can respectively trigger an APF thyristor and a thyristor in the thyristor control reactor set. The scattered power generation reactive compensation device with the harmonic suppression function can effectively restrain resonance between the passive filter and the power grid, enables harmonic compensation accuracy to be higher and system response to be quicker, improves reactive compensation safety and is economical and practical.