China Detains American Scientist on Espionage Charges as US Demands His Release

An American seismologist who specializes in monitoring underground nuclear tests has remained in Chinese custody for more than 18 months, with the United States calling for his immediate release amid rising tensions between Washington and Beijing.

Youlin Chen, a US-based scientist who lived in Boston, has been detained in China since November 2024 on espionage allegations. His supporters, family and US officials insist he has been wrongfully imprisoned, arguing that his work has always been conducted openly for scientific and research purposes.

US Senator Edward Markey confirmed the detention in a statement on Tuesday, while Global Reach, a US non-profit assisting Chen’s family, said President Donald Trump personally raised the issue with Chinese President Xi Jinping during their meeting in Beijing in May. Despite that appeal, Chen remains in detention.

The case has added another layer of strain to already delicate US-China relations ahead of Xi’s expected visit to the United States later this year. Chen is currently the only American in China officially designated by the US government as being “wrongfully detained,” according to Global Reach.

Chen’s research focuses on using seismic data to detect and monitor underground nuclear explosions, including North Korea’s nuclear tests. His studies have received funding from the US State Department and the US Air Force Research Laboratory. A 2020 technical report authored by Chen analysed seismic data from stations across Asia, including China, to improve methods for identifying underground nuclear tests, while a follow-up study published in 2024 further expanded that work.

Supporters believe his detention may be linked to concerns surrounding China’s nuclear programme. Global Reach suggested authorities may suspect his research is connected to allegations that Beijing conducted an underground nuclear test in 2020, an accusation China has consistently denied.

Chen was reportedly arrested at Beijing airport after visiting his parents. He was formally charged with espionage on May 1, 2025, but has yet to stand trial. Global Reach described the case as an example of “hostage diplomacy,” claiming the scientist is being used as leverage amid broader geopolitical competition between China and the United States.

China’s Foreign Ministry rejected claims that Chen was being wrongfully detained, insisting the country’s judicial authorities are handling the case in accordance with Chinese law. The US State Department, however, said it has repeatedly raised the matter with Beijing and continues to demand Chen’s immediate release.

Chen’s wife, Yufang Rong, said she has not spoken privately with her husband for more than 600 days and fears for his health. She maintained that Chen never held a US government security clearance and argued that his research was transparent and carried out in collaboration with Chinese scientists. Rong also disclosed that Chinese investigators have questioned her husband more than 100 times about his research into North Korea’s underground nuclear tests.