The invention discloses a method for measuring the lost gas content in a test of the gas content of shale, and provides a technical path for more accurately calculating the lost gas content in the gas content of the shale. The method comprises the following steps: measuring the volume of a rock core sample; putting the rock core sample into a first container, and filling holes in the first container with a filler; sealing the first container, putting the sealed first container into a second container, and setting an equilibrium temperature of the second container as a wellhead circulating temperature; continuously measuring the gas flow flowing out of the first container and the temperature in the first container for multiple times; setting the stationary temperature of the second container as a bottom hole temperature, and continuously measuring the gas flow flowing out of the first container and the temperature in the first container for multiple times until no gas flows out of the first container; calculating the lost gas content in a process from the rock core sample reaching a wellhead to sealing the first container; calculating the lost gas content in a process from starting drilling to the rock core sample reaching the wellhead; and obtaining the total lost gas content, namely the sum of the two lost gas contents.