一般認為，使用不同的系綜來處理同一個物理系統時仍能得到相同的物理量，但在近年來的研究顯示，此一現象並不一定成立。
本篇論文主要是在探討系綜不等價的現象，我們討論了該現象發生的機制，並引用兩個簡單的模型來了解系綜不等價的現象，此外，我們檢驗了Ising模型在微正則系綜與正則系綜間的等價性，並得到Ising模型在此二系綜間不等價的結果。

In statistical mechanics, the same equilibrium properties can be obtained by applying different ensembles to calculate the same physical system. However, some authors recently demonstrated that the argument is not necessary to be true for all systems.
In this thesis, we would like to discuss the mechanism of the phenomenon in which the predictions obtained are nonequivalent. We also introduce an example of two simple models in order to reexamine whether their ensembles are equivalent. In addition, we study on the Ising model in microcanonical ensemble and canonical ensemble to illustrate that the results obtained by using these two ensembles are nonequivalent.

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