It is critically important to maintain long-term adequacy for power systems. With market rules， bidding strategies and investment strategies of market participants being represented as experimental environment， this paper studies long term dynamics of generation capacity adequacy by using dynamic simulations of investment market interacted with power market. Mechanisms of long term oscillation of the generation capacity adequacy are explored. The influences of generation capacity construction delays， surveillant approval to augment new capacity and game strategies of the investors on the oscillation cycle， swing magnitude and market concentration index are investigated， which is helpful to keep power market and power system healthy.