Abstract: For study the influence law of the urban space structure on the automobile exhaust diffusion，the paper established an urban core region geometry model from high resolution remote sensing image． Based on the important boundary conditions meteorological wind，using CFD and multiphase flow，the diffusion processing of the vehicle queue exhaust at a crossroads during idle waiting of 35s，45s、55s were simulated，and the volume fractions of four monitoring stations at 45 seconds were measured． At last，building heights were optimized and the automobile exhaust contents reduced． Some conclusions were as follows: in narrow space，CO volume fraction near-earth space was up to 1. 0 × 10 － 7， and more than 100 times of the entire study area average value． Urban space structure had great influence on automobile exhaust diffusion． The laws deduced from simulation agree with the measurement． Local meteorological wind direction and speed should be considered and some height gradient should be selected in buildings structural layout，promoting the exhaust spread rapidly to the urban remote space．