The invention relates to a visualized natural gas hydrate simulation test device and a method. The visualized natural gas hydrate simulation test device comprises a high-low temperature test box, a high-pressure reaction kettle, a charging system, a gas pressurizing system, a separation system, an imaging system, a magnetic stirring system and a data acquisition and processing system, wherein the high-pressure reaction kettle is arranged in the high-low temperature test box; the charging system is connected with a charging hole of the high-pressure reaction kettle; the gas pressurizing system is connected with a gas inlet of the high-pressure reaction kettle; the separation system is connected with a gas outlet of the high-pressure reaction kettle; the imaging system is arranged at the upper end of the high-pressure reaction kettle; the magnetic stirring system is arranged in the high-pressure reaction kettle; the data acquisition and processing system is used for monitoring the internal temperature and pressure of the high-pressure reaction kettle and monitoring the flow of the gas inlet and the gas outlet of the high-pressure reaction kettle. According to the device and the method, the temperature and pressure conditions of a true sea deep well can be simulated, and the internal temperature and pressure of the reaction kettle can be accurately monitored; by the data acquisition of a computer, the thermodynamic change during hydrate generation and decomposition can be monitored in real time, so that the rheological parameters of a drilling fluid are accurately measured. The device is easy to operate and high in measurement accuracy, and can be widely applied to the rheological property measurement process of various drilling fluids.