Li was last seen on Friday, 20 September at around 10pm at his address in Orrysdale Road, West Kirby.
Li is described as Asian, around 5ft 8in tall, slim build with black hair and brown eyes. He is believed to be wearing a grey Lonsdale tracksuit, a grey Slazenger polo short, a grey Regatta rainproof jacket and red Adidas PT trainers.
Li is not thought to have any links to the Merseyside area and officers believe it may be possible that he has travelled another part of the UK.
Officers would ask Le or anyone who has seen him since Friday, 20 September to contact 101 or contact Missing People on 116 000.