The invention discloses a natural gas hydrate drilled core light hydrocarbon gas content analysis test system and a method. The analysis test system comprises a temperature control cavity, wherein a weight calculation part is arranged in the temperature control cavity; a sealed decomposition chamber is placed on the weight calculation part; a gas inlet one-way valve and a gas outlet gas circuit switch are respectively arranged on a gas inlet and a gas outlet of the decomposition chamber; a pressure meter and a safety valve are also arranged on the decomposition chamber; an air source is connected with the gas inlet one-way valve through a first fast gas circuit connector; the gas outlet gas circuit switch is connected with a gas inlet of a gas collecting chamber through a second fast gas circuit connector; a gas outlet, an air source and a hydrogen source of the gas collecting chamber are respectively connected with a corresponding gas inlet of a hydrogen flame ionization detector; a gas taking port is also formed in the gas collecting chamber. According to the natural gas hydrate drilled core light hydrocarbon gas content analysis test system and the method provided by the invention, a hydrate is controlled at low temperature so as to be decomposed, and the hydrogen flame ionization detector is used for directly measuring and analyzing light dydrocarbon gas volume, so that the accurate measurement on light dydrocarbon gas content in a natural gas hydrate reservoir drilled core is realized, the technical difficulties and the safety risks caused by low decomposition temperature, fast speed, and large release gas volume are overcome, and the system and the method are safe and practical.