The utility model relates to a testing device for generating and decomposing natural gas hydrate, comprising a liquid supply module and a gas supply module, wherein the liquid supply module and the gas supply module are connected with two inlets of a natural gas hydrate generating and mining simulation module respectively by pipelines; the generating and mining simulation module is arranged in an environment simulation module; the outlet of the generating and mining simulation module is connected with a metering module by a back-pressure control module; and the metering module, the generating and mining simulation module, the gas supply module and the liquid supply module are connected with a data collecting module. In the utility model, a plurality of pressure sensors, thermocouples and electrodes are arranged on the pipe wall of a model pipe; all pressure sensors, thermocouples and electrodes are used for measuring the generating and decomposing process of the natural gas hydrate in the model pipe and sending the values of all testing points to a data collecting module; therefore, the monitoring on the synthesis quantity of the natural gas hydrate and the changes of the basic substance parameters are realized. The testing device can be widely applied to various detection fields of generating and decomposing of natural gas hydrate.