China claims self-ruled Taiwan as its territory and has ramped up military and political pressures on the democratic island in recent years.

The two sides split in 1949 after a civil war and have been spying on each other since.

The defendants in Thursday's sentencing were active-duty soldiers "willing to collect intelligence for China that caused the leak of important secrets," a Taiwan High Court statement said. "They were seduced by money."

Among them was a man surnamed Hsiao, who was the key to recruiting soldiers to join "a network for China" to gather and hand over information, the court said.

He received the heaviest jail term: 13 years.

Another was sentenced to five-and-a-half years for shooting a "psychological warfare video to indicate his willingness to surrender to the People's Liberation Army", while one man received a nine-year sentence for "conspiring to defect" to China by flying a military helicopter.

"Their actions violated their official duties of being loyal to the country, defending the country and the people... to seriously endanger national security and the well-being of the people of Taiwan," the court said.

All eight men can appeal the ruling.

Prosecutors had initially indicted 10 people in November in the case. One was acquitted due to a lack of evidence.

The other -- a retired soldier surnamed Chen -- was identified as the person who enlisted Hsiao.

But the court said it would handle Chen's case separately after he fled to China. He is currently wanted in Taiwan.

Thursday's sentencing was the latest in a recent string of spying cases.

Last month, a sergeant who worked at a navy training centre was indicted for allegedly photographing and leaking confidential defence information to Beijing.