Police say Chen is diagnosed with schizophrenia and has not been taking his medication.
Chen was last seen in the area of 29th and Parnell. He may be headed to Midway or O'Hare airports. He has said that he wants to go to China.
Chen is 5 feet 4 inches tall, weighs 132 pounds and is Asian.
Anyone with information is asked to contact the Area Central Detective Division at (312) 747-8380 or call 911.