The invention provides a mixed spraying device for detecting properties of an accelerating agent for sprayed concrete. The mixed spraying device comprises a spray nozzle body, a cement paste storing chamber, a gas-liquid mixing chamber and an accelerating agent spray head; the two ends of the spray nozzle body are provided with an expansion port and a limiting necking port correspondingly; a cement paste feeding connector is installed on the outer wall of the cement paste storing chamber; a detected accelerating agent feeding connector and a compressed air connector are installed on the outerwall of the gas-liquid mixing chamber; the limiting necking port, the cement paste storing chamber and the gas-liquid mixing chamber are sequentially connected end to end; and the accelerating agent spray head is connected with the top of the cement paste storing chamber through a thread pair and arranged in the limiting necking port of the spray nozzle body. According to the device, the detectedaccelerating agent and the appropriate flow of compressed air are mixed and spray-atomized and then fully mixed with cement paste, and finally conditions are created for jet compact molding in a conical test mold. The device is a matching component of a device for detecting the properties of the accelerating agent in a jet compact molding mode.