Information minister Mohan Bahadur Basnet inaugurated the link in a ceremony in the capital, Kathmandu.
The optical fiber line crosses into China from the Rasuwagadhi border point, northwest of Kathmandu.
Until Friday, landlocked Nepal's only internet connections were through three access points in neighboring India. China is providing an additional route to the global internet.
Nepal is covered on three sides by India, which has extensive influence on its economy and politics. China and Nepal share a border covered with high mountain peaks.
Work on a communications link to China was completed in December 2014, but it was completely destroyed in a devastating earthquake in April 2015. A land transportation route through the Tatopani border point to China is still closed.
China has helped build highways, communication systems and hospitals in Nepal.