Historically,ancient China was an advanced country.But before the birth of a new China,it became one of the poorest and most backward country in the world.One of the most reasons is the long term self-fettered.Realistically,recent world is an open world and closed-door economic development can not success.Morver,China's opening-up has been lasting almost 20years.\National economy has been growing repidly,and people's material life has improved obviously. Historically,ancient China was an advanced country.But before the birth of a new China,it became one of the poorest and most backward country in the world.One of the most reasons is the long term self-fettered.Realistically,recent world is an open world and closed-door economic development can not success.Morver,China's opening-up has been lasting almost 20years.\National economy has been growing repidly,and people's material life has improved obviously.