The new midpoint rate is 0.23 percent weaker than Friday's rate of 6.8655 yuan per dollar.
The bank devalued the yuan by 3 percent in August 2015, sending shockwaves throughout stock markets. Three further major devaluations followed in early 2016, in July, when the rate sunk to 6.67 yuan per dollar, and again in October.
Pundits said this was an effort to boost exports, while the government denied the claims. The devaluations have led to US President Donald Trump calling China a "currency manipulator" and sparked fears of a trade war.