Abstract: Thermocompression simulation experiment of hydrocarbon generation and expulsion is one of the main instruments for the study of hydrocarbon thermal evolution mechanism.The existing simulation methods consider more about temperature,pressure and time rather than pore fluid pressure,hydrocarbon generation room,high temperature and pressure liquid water as well as the first hydrocarbon expulsion.With self-developed formation porosity thermocompression simulation experiment instrument,taking into consideration of various factors,the author has set up a formation porosity thermocompression simulation experiment of hydrocarbon generation and expulsion.It has been found out,as the same as temperature and time,pressure,hydrocarbon generation room as well as high temperature and pressure liquid water affect the evolution of hydrocarbon generation from sedimentary organic ma-tters through the whole process,only different in forms and manifestations during different stages of evolution.From low-mature to mature stage,the main impact of formation porosity high temperature and pressure liquid water system on hydrocarbon generation from type Ⅰ kerogen black mud are de-laying oil generation,inhibiting gas generation,changing kerogen composition characteristics and en-hancing the hydrocarbon generation potential of source rocks.