It　remains　unknown　whether　exposure　to　ambient　air　pollution　can　be　a　mediator　linking　socioeconomic　indicator　to　health　outcome.　The　present　study　aims　to　examine　the　mediation　effect　of　PM2.5　air　pollution　on　the　association　between　urban-rural　division　and　the　incidence　(mortality)　rate　of　male　lung　cancer.　We　performed　a　nationwide　analysis　in　353　counties　(districts)　of　China　between　2006　and　2015.　A　structural　equation　model　was　developed　to　determine　the　mediation　effect　of　exposure　to　PM2.5.　We　also　tested　whether　the　findings　of　the　mediation　effect　of　exposure　to　PM2.5　are　sensitive　to　the　controls　of　smoking　factors　and　additional　air　pollutant,　and　PM2.5　exposures　with　different　lag　structures.　According　to　the　results,　we　found　that　exposure　to　PM2.5　significantly　mediated　the　association　between　urban-rural　division　and　the　incidence　rate　of　male　lung　cancer.　Specifically,　there　were　significant　associations　between　urban-rural　division,　exposure　to　PM2.5,　and　the　incidence　rate　of　male　lung　cancer,　with　PM2.5　exposure　accounting　for　29.80%　of　total　urban-rural　difference　in　incidence　rates　of　male　lung　cancer.　A　similar　pattern　of　results　was　observed　for　the　mortality　rate　of　male　lung　cancer.　That　is,　there　was　a　significant　mediation　effect　by　PM2.5　on　the　association　of　the　mortality　rate　with　urban-rural　division.　The　findings　of　exposure　to　PM2.5　as　a　mediator　were　robust　in　the　three　sensitivity　analyses.　In　conclusion,　urban-rural　difference　in　exposures　to　PM2.5　may　be　a　potential　factor　that　contributes　to　urban-rural　disparity　in　male　lung　cancer　diseases　in　China.　The　findings　inform　that　air　pollution　management　and　control　may　be　effective　measures　to　alleviate　the　great　difference　in　male　lung　cancer　diseases　between　urban　and　rural　areas　in　China.