This paper tries to reassess the main reasons of Cần vương (Aid the King) movement which had took place against the French colonization at the end of 19th century. Whereas the precedent researches had regarded the lack of a coherent national structure and the inferiority of weapons as fatal, the paper attempts to figure out more fundamental factors in the political arena of the royal palace and from the socio-religious conflicts in the countryside. Before the outbreak of Cần vương movement in July 1885, the political disorder in the Hue Imperial Court had insinuated that the Nguyễn dynasty was no longer thoroughly consistent to meet foreign invasion strongly. The plot of ‘Three Kings during Four Months’ in 1883 and the crippled succession to the throne had the young kings lose their dignity not only in dealing with the leading mandarins in the Court but also in taking command of the Cần vương insurrection troops. The sacrosanctity of the Dowager Empress Từ Dũ, the mother of Tự Đức, had restrained the young kings from regaining their authority from the old mandarins on the one hand and had been incapable of restricting the leading mandarins to abuse their power in the leading process of the Cần vương movement. The Council of the Chancellors for the young kings had empowered the three leading mandarins like Trần Tiến Thành, Nguyễn Văn Tường and Tôn Thất Thuyết to dabble in palace intrigues and to flee from the battle line spontaneously. However, more serious dangers to the Cần vương movement had begun to grow in the hearts of main troops who had been supposed to aid the king Hàm Nghi. The Vietnamese confucian scholars who had been disappointed at the languid Imperial Court against the French invaders and the Vietnamese Catholics had become demoralized in the front and had been more hostile to the compatriotic Christian villagers than to the French soldiers. The Vietnamese Catholics who had consisted of literary elites, mandarins, merchants, soldiers and peasants and who had become conscious of the egalitarian social values and order should have been persecuted by the Court’s ban on the religious activities and by the confucian scholar’s oppression. Ethnic tribes such as Mường, Thượng, Thái, Mán, Mèo, Nùng and Thổ who had been discriminated from the outset of the Nguyen dynasty might have been quite at a loss when they were invited to participate in fighting against the French for their own exploiters. The long term accumulation of contradictory relationship between the Vietnamese ruling class and the ruled had have ill effects on the traditional resistance operations and eventually had driven the country to lie under the French colonial rule.