To meet the requirements of light duty vehicle regulation test and research emission test, host computer system was developed. Hardware was designed based on virtual instrument architecture. Software was designed with unified modeling language. Function of data acquisition, flow control and data processing for light duty vehicle bag sampling, continuous dilution sampling and direct sampling were realized. Application in practice showed that the system, with all-around testing performance, reliable control and exact data, is fit for exhaust tests on light gasoline or diesel vehicles.