近幾十年來的台灣，政治舞台上一直是由兩大政黨扮演主角。然而，兩大政黨支持者意識形態的嚴重分歧，導至在政黨政治的發展過程中，蒙上一層情緒化、不理性的陰影。本研究乃選擇了社會認同理論(Social Identity Theory)做為論文的理論依據，企圖探討這些問題。本研究目的是探討國內兩大政黨的支持者，如何形成其政黨認同，以及對政策的判斷是否受認同團體的影響而有所偏差。研究方法的使用，除了設計一問卷，來了解兩大政黨不同的意識形態，並企圖驗證台灣地區人民對於政策好壞的判斷，是否受其政黨支持屬性所左右。另外，在文獻的探討過程中，也對兩團成員的認同發展，做了一些探索與推論。前一部份符合心理學科學實驗的典範，後一部份則檢示歷史的發展，偏重於邏輯的推理。在實徵研究方面，分成兩個部分。研究一是使用一份自編的政黨意識形態問卷，施以大樣本問卷調查，比較兩大政黨支持者所具有的不同意識形態，以及不同的族群自我定義。研究二以一個實驗操弄來驗證內團體偏私現象。研究結果發現，新的族群分類方式正在取代原有的省籍分類，一種抽象的族群自我定義：「台灣人是台灣人」和「台灣人是中國人」的二分法，將台灣地區的人民劃分為兩個新族群。這兩個新族群恰與兩大政黨意識形態相符。另外以本省人和外省人為主的省籍情結並未消失，它只是轉化為上述的兩種抽象定義。因此，省籍的背景，加上個人對中國文化的信仰程度，決定了一個人的政黨認同取向。而一個政黨意識形態較強的人，在對政策的態度上，常常不知不覺的受到己團體意見所左右，而不能客觀地判斷政策的優劣。尤其以民進黨意識形態者所產生的這種內團體偏私較強，國民黨意識形態者的內團體偏私現象則較不明顯。最後，根據本研究的結果，對台灣政治生態發展所做的建議是，唯有將台灣意識或中國意識視為一種文化意識，而非族群意識。台灣地區人民才可能將族群認同與政黨認同分開 ，並發出理性的政黨認同，與團結的國家認同。 / There are two major political parties that play important roles in the scene of Taiwan politics. The KMT have government Taiwan area over fifty years, which came from mainland China. Being a minority group as opposed to the KMT, the natures of the DPP supporters are not as same as the members of the KMT. Their ancestors have lived in Taiwan for hundreds of years. Consequently, the ethno identity and the political identity are confused with each other for most of the people in Taiwan. Someone would choose suort one political group not because their cognition to politics, but because most their ethno background. It is to say, one whose fathers came from mainland china would mostly support the KMT than the DPP. One whose fathers were birth in Taiwan is mostly support the DPP than the KMT.The purpose of research is to find out the difference of ideology between two political groups. Besides I will utilize the real- life intergroup relationship for proving in-group bias. Two methods of research were adopted. One is historical research, and the other is an experimental method. The results reveal that there were different ideology in two groups. The KMT supporters usually have more conservative attitudes about politics. The DPP supporters have more open attitudes with their opinions. The ethno backgrounds usually display the role of accentuation. On the other hand, The in-group bias phenomenon has been partly proved. It means that there is a vivid in-group bias phenomenon in minority group. Someone who supports the DPPave a higher rating with the statement that talked by the DPP member. The conclusion of the research also reveals something. There were two opposed opinions rising to explain someone's identification for their sense of belonging. What opinions someone may choose are usually decided by their political identity. One who supports the KMT choose more likely the opinion "Taiwanese is also a Chinese." One who supports the DPP accept more likely the opinion "Taiwanese is just a Taiwanese." Because the two opinionsre abstract definition, so they are not decided by someone's descent. That is to say the traditional manners of ethno category by dialect are broken. The new manner of ethno category is not imposed by someone's descent. I am not optimistic about the phenomenon. The rise of the new ethno definition does not only completely displace the old system of category but also confused with each other. It must have the Taiwan people divided into more small groups. So I predict in the future, The ethno identity of Taiw people would be more complicated .