“Loyal to the King” is the supreme principal in oriental society that everyone had to obey, especially confucian scholar. And it is the same in Vietnam, in particular in Le-So period, Confucian education had a large amount of doctors who had both talent and virtue, both patriotism and loyal to the king that completed the government official system. Because of these loyal and gifted doctor staffs that had a main part for the cause of national construction and development, Dai Viet had been changed to the phase of quite prosperous of Vietnam feudal system. However, in the 17th - 18th century, the large change of politics, economy, society and culture made “loyal” have no sufficient meaning as before.