The invention provides a broadband frequency agility millimeter wave frequency synthesizer. The broadband frequency agility millimeter wave frequency synthesizer comprises a reference source module and a millimeter wave frequency conversion module which are in interconnection through a cable, wherein the reference source module is used for providing intermediate frequency and local oscillator signals for the millimeter wave frequency conversion module. The broadband frequency agility millimeter wave frequency synthesizer is advantaged in that a scheme of the hybrid frequency synthesis technology, namely a DAS+PLL scheme is employed, through combination of the two, advantages of wide frequency band of PLL and low phase noise of DAS are fully utilized, a path of Ku wave band local oscillator signal and three paths of millimeter wave emission signals having a certain isolation degree are provided, and the provided signals can be taken as an emission excitation signal of the present machine and a local oscillator signal of a receiver.