The invention belongs to the coalbed gas exploitation field and particularly relates to a coalbed biogas accumulation process simulation device and an experiment method. The device comprises a biogas generation and storage system for simulating interaction between a coalbed and bacteria liquid, a pressure control and monitoring system used for simulating and controlling coalbed burying depth, a bacteria liquid circulation and biogas detection system used for simulating and observing methane gas amount generated in the coal reservoir, gas component and isotopc analysis and methanometer activity assay, and a temperature regulation system used for realizing biogas generation and storage system thermostatic control, wherein the pressure control and monitoring system, the temperature regulation system and the bacteria liquid circulation and biogas detection system are connected with the biogas generation and storage system, and the pressure control and monitoring system and the temperature regulation system are externally connected with a host computer. The device is advantaged in that the biogas generation accumulation process along with coalbed uplift and descent can be detected, through pressure change, temperature control and bacteria liquid injection of the coalbed, coalbed biogas generation and occurrence rules are simulated.