Due to the deterioration of the Earth's environment, many governments around the world strengthen vehicles emission regulation more and more strictly. In order to measurement vehicles exhaust emissions on the real road situation. We establish a Simple Emission Measurement system (SEMS) to detect the amount of real time emission. The SEMS use stoichiometric theory to predict fuel consumed, accumulated CO2 and NOX mass by detect NOX volume concentration, O2 volume concentration and exhaust air flow rate. The Simple Emission Measurement system has been validated by engine test using ESC (European Stationary Cycle) and ETC (European Transient Cycle) test procedure, and the result shows the error of emission data is about ± 10% compare to the emission analyzer in the vehicle testing laboratory.