How did the Song Dynasty end?

Well, as we all know, everything has to go to end after a long term. It is the first reson for the end of Song Dynasty. A dyasty will not be in rule forever.
Secondly, although generally no fatuous and tyrant rulers were in charge of the Song Dynasty, there were traitors. The notorious two are Qin Gui and Jia Sidao, who help other tribes to attack the Song Dynasty. After a long time batter, flighting with Mongolia Nationality and King Nationality then, the Song Dynasty finally could not stand as steadily as it usually did.

The Southern Song's regime was subject to the Jin. Many patriotic generals were killed in the late period. In 1279, the army of the Yuan Dynasty captured Lin'an, putting the Southern Song to an end.

Actrually, the economy in Southern Song Dynasty is far more advanced than the other states like Yuan (Mongoloid), the Jin (Jurchens), but its national defence capability is very poor. South Song Dynasty is a country which admires literature, and its interdenominational fight killed many partriotic generals, finally the Yuan Dynasty captured Lin'an, putting the Southern Song to an end.

The Song dynasty came to an end when they allied with the Mongols against their longtime enemies, the Jin. The Mongols helped them to conquer the Jin, but then turned on the Song. The leader of the Mongols, Kublai Khan, conquered all of China and began his own dynasty, the Yuan dynasty.