The sentence for Raef Badawi was handed down in a Jeddah court.
Badawi was arrested last June and sentenced to seven years in jail and 600 lashes. But an appeals court overturned the ruling and ordered a retrial.
In addition to a harsher sentence, the court also ordered Badawi to pay a $266,000 fine.
The network that he co-founded with another activist, Suad al-Shammari, had declared May 7, 2012 a "day of liberalism".
Shamari said the network's website had "criticised some clerics, the Commission for the Promotion of Virtue and Prevention of Vice (religious police), in addition to religious fatwas (edicts) considered harmful to Islam.
"Clerics have filed a lawsuit against him. The government tries to appease them, at our expense sometimes," AFP reported her as saying.
Shamari said the network was only active online, adding: "Our activities remain virtual."