By Lingling Wei

BEIJING--A respected official who played a key role in managing China's $3.8 trillion in foreign-exchange reserves has resigned, according to China's foreign-exchange administrator.

A representative for China's State Administration of Foreign Exchange said Tuesday that Zhu Changhong had resigned as the agency's chief investment officer. His mission at the agency was set to wrap up at the end of January, the representative said in a statement to The Wall Street Journal.

Mr. Zhu played "an important and outstanding role" in managing China's foreign-exchange reserves, the representative said. She declined to comment further.

Mr. Zhu declined to comment and referred questions to SAFE.

Mr. Zhu formerly was a senior executive at investment firm Pacific Investment Management Co., or Pimco, before joining SAFE in late 2009.

Write to Lingling Wei at lingling.wei@wsj.com