The invention discloses a device and a method for measuring the content of gas in engine cooling liquid. The measuring device comprises a water inlet pipe, a gas separation cavity, a measuring cylinder and a water outlet pipe, wherein the water inlet pipe is connected with a cooling system of an engine; the gas separation cavity is in a cone shape, the cross section area of the gas separation cavity is larger than that of the water inlet pipe, and one end of the gas separation cavity is communicated with the water inlet pipe; the measuring cylinder is fixedly arranged at the top of the gas separation cavity, and a switch is arranged at the top of the measuring cylinder; one end of the water outlet pipe is communicated with the other end of the gas separation cavity, the inner diameter of the water outlet pipe is less than that of the water inlet pipe, and the water outlet pipe is provided with a flow meter and a pressure meter. The measuring device and method can be used for accurately measuring the content of gas in cooling liquid in different cooling system design schemes so as to conveniently analyze the advantages and disadvantages of the different cooling system design schemes; cooling liquid enters an engine cooling system again from the water outlet pipe of the measuring device and the content, the flow speed and the like of the cooling liquid of the cooling system are not influenced.