The rainbow schlieren can be widely used in a lot of typical flow field as a non-invaded optical measurement. It can measure the density and density-grads quantitatively. The rainbow schlieren experiment takes the axis-symmetry free jet as a object, using the typical “Z” schlieren system and Xe-lamp, and replaces the edge with rainbow filter. The facture and calibration of rainbow filter, the quantitative measure theory, and the date processing are studied in detail. While the freejet of this expriment is simulated, and a accordant result is obtained. The technology supports a reference to the quantitative visual study of the flow measurement.