The countermeasures of city carbon emission reduction have been put forward based on the multi-level urban carbon emission reduction mechanism and multidisciplinary complex system science city carbon emission regulation mechanism. These countermeasures include the following aspects: giving governments on directing functions as well as market on leading role; strengthening innovation and integration technology, systems and concepts; speeding up upgrade of urban industry structure, building low-carbon consumption environment and advocating low-carbon consumption concept as well as promoting the urban development toward a low-carbon economy.