The invention provides a conical beam CT synchronous control device and a control method thereof and belongs to the field of CT control devices. The conical beam CT synchronous control device comprises a radiotherapy analog machine host, a high pressure generator, a programmable controller, a synchronous interface board, a flat panel detector and an image collection computer; the input end of the programmable controller is connected with the signal output end of the high pressure generator through the synchronous interface board, the output end of the synchronous interface board is connected with the input end of the high pressure generator through the synchronous interface board and the input end of the radiotherapy analog machine host, a serial port of the programmable controller is connected with the image collection computer through a communication cable, and the flat panel detector is connected with the image collection computer through a network cable for completing synchronous control over the three activities, namely beam outputting of the high pressure generator, rack angle sampling at the moment of beam outputting and image acquisition at the moment of beam outputting.