The invention discloses a power transmission system power adjustment system, comprising one or more power adjustment module, wherein the power adjustment module is connected with a reactive power control wire outlet port of a bus; an input end of the bus is connected with a wire inlet port; each power adjustment module comprises a pre-allocation power device and at least one static var generator.Power adjustment is carried out in the following mode of obtaining a reactive power adjustment objective according to an adjustment and control objective; configuring pre-power allocation amount; deploying the pre-allocation power device to carry out fixed value reaction power adjustment on a power grid; obtaining power adjustment vacancy according to the allocation condition and carrying out tracking adjustment on the power grid through the static reactive power generator. The system is a multi-DFACTS device coordinative control system applied to an active power distribution network. Switch states and measurement data of DFACT devices are collected in real time. Real-time coordination is carried out according to the adjustment and control objective. The power adjustment stability of a power transmission system is improved.