Jerry Chun Shing Lee, 54, was approached in 2010 by two Chinese intelligence officers who offered to pay him $100,000 and to take care of him "for life" for information he had acquired as a CIA officer, according to a Justice Department statement. Lee left the CIA in 2007 and moved to Hong Kong.
Hundreds of thousands of dollars were subsequently paid into Lee's personal bank account between 2010 and 2013, according to the statement.
The statement said Lee had created thumb drives containing secret information about CIA activities and the location and time frame of a sensitive operation.
An FBI search in 2012 of a Honolulu hotel room registered to Lee also discovered handwritten notes by him about his work as a CIA officer before 2004.
"These notes included, among other things, intelligence provided by CIA assets, true names of assets, operational meeting locations and phone numbers, and information about covert facilities," the statement said.
U.S. Assistant Attorney General for National Security John Demers said it was the third case in less than a year in which a former U.S. intelligence officer had pleaded guilty or been found guilty of conspiring to pass defense secrets to China.
"Every one of these cases is a tragic betrayal of country and colleagues," he said in the statement.
Lee's sentencing is set for Aug. 23 and he faces a maximum penalty of life in prison.
In March, a former U.S. Defense Intelligence Agency officer, Ron Rockwell Hansen, pleaded guilty attempting to transmit classified information to China and receiving hundreds of thousands of dollars while acting as an agent for Beijing.
Last June, another former CIA case officer, Kevin Mallory, was convicted on espionage charges for passing classified documents to China.
This week, FBI Director Christopher Wray said China posed the biggest threat to the United States when it came to economic espionage.
Last month, the Justice Department said a former engineer and a Chinese businessman had been charged with economic espionage and conspiring to steal trade secrets from General Electric in a scheme for which the Chinese government provided "financial and other support."