Since the middle of the 18th century, Sinkiang (= Eastern Turkistan) had been ruled by Ch'ing Dynasty. After the Chinese Revolution in 1911, the Han Chinese rulers continued an administration which was an ossified version of the Imperial administration. The local Turkic-speaking Muslims rose against the Han Chinese rulers in 1931, and finally established a separate "Islamic Republic of Eastern Turkestan" at Kashgar in 1933. Their activities during this period have been treated as ancillary in the history of political events, or regarded as the result of the influence of the foreign ideologies. In this paper, the author attempts to clarify the actual situation of their activities in the Muslim rebellion in the early half of the 1930s by discussing the secret organizations which led the revolts, and to examine the character of the nationalism of the Turkic-speaking Muslims in Sinkiang. During the 1910s and 1920s, the Turkic-speaking bourgeoisie and progressive 'ulamas started and developed he reformist movements all around Sinkiang, which were blocked by the oppression of the Han Chinese officials and conservative 'ulamas. During the early half of the 1930s, at Turfan and Khotan the Muslims rose up in. rebellion to overthrow the Han Chinese authorities under the control of secret organizations formed by the bourgeoisie and progressive 'ulamas. At Turfan, the leaders of the revolt aimed to modernize Sinkiang and to protect it from the influence of U.S.S.R. However, they were defeated. On the other hand, at Khotan the secret organization played an important role in achieving its aim to sweep away the Han Chinese authorities through a "sacred war". The rebellion leaders, basing their nationalism on Eastern Turkistan, generally aimed to set their "motherland" (=Eastern Turkistan) free from the rule of the Han Chinese authorities, but their thought and activities concerning the formation of a separatist policy at that time varied according to differences in their understanding of the external situation. And it is important to note that the activities for establishing the independent state of the Turkic-speaking people and the proposal for provincial autonomy emerged from within these leaders. On the other hand, their inclination toward the reforms contained two forms. Their aim to modernize local society were partially sttemed from their feeling that they were being ruled by the uncivilized Han Chinese, which strengthened their desire to overthrow the Han Chinese authorities. But they found it difficult to actually carry out the reforms because of political fluctuations. In contrast, the reformist policy adopted by the new Khotan government established under the leadership of the 'ulamas after the successful rising had a tendency to strengthen the Islamic character of local Khotan society. However, such movements were frustrated when the "Islamic Republic of Eastern Turkestan" which was the fruit of the separatist activities of the Turkic-speaking Muslims was dismantled, and the rule of the warlord Sheng Shih-tsai was established in 1934.