- Video report by ITV News China Correspondent Debi Edward
Chinese President Xi Jinping hailed the start of a "new era" as he set out his vision for China to become a "great modern socialist country".
Opening the national congress, Mr Xi urged the Communist Party to take a stronger role in society and economic development to better address "grim" challenges facing the country.
"The great rejuvenation of the Chinese nation is no walk in the park or mere drum-beating and gong-clanging.
"The whole party must be prepared to make ever more difficult and harder efforts."
"To achieve great dreams there must be a great struggle," Mr Xi told delegates at the congress, which takes place once every five years.
Mr Xi, who is expected to get a second five-year term as party leader, also paid tribute to China's achievements.
He hailed island-building efforts in the disputed South China Sea as well as the "One Belt, One Road" infrastructure investment project aimed at improving connections between China, Europe and Africa.
The president also praised the party's increased grip over domestic security, saying social stability had been maintained and security strengthened.
Mr Xi pledged that the party would have "zero tolerance" for corruption and said it would "continue to purify, improve and reform itself".
He also drew a hard line on sovereignty, saying that the party must "staunchly oppose all efforts to split China" or to undermine ethnic relations.
Mr Xi also pledged to make the banking industry more market-oriented and to reduce bloated state-owned steel and coal industries.
The flood of low-cost Chinese exports has strained trade relations with the US and Europe.
They have been blamed for depressing global prices for steel, aluminium and other goods, as well as threatening jobs abroad.