Abstract: Expanded ginseng yam products were prepared by twin-screw extrusion process,and the best process and the changes of physical and chemical properties before and after extrusion were studied. Taking raw sun-dried ginseng and yam decoction pieces as experimental materials,the raw sun-dried ginseng powder and yam decoction piece powder were mixed according to the ratio of 1:1. The radial expansion rate of the expanded product was taken as the inspection index,the L₉(3⁴)orthogonal table was used on the basis of single factor to optimize process parameters of ginseng yam blend. And the nutritional quality,physical characteristics and effective components before and after expansion were compared and analyzed.The results showed that the optimum technological conditions were screw speed 250 r/min,Ⅲ area temperature 160 ℃ and moisture content 24%. Under these conditions,loose and porous expanded products could be obtained,and the radial expansion rate of the products reaches the maximum value of 2.43. Compared with the nutritional components before and after extrusion,there was no significant difference in crude ash content(P>0.05),but the crude fat,TDF,IDF,crude protein,soluble protein,total starch and amylopectin content all decreased(P<0.05). Soluble dietary fiber and amylose increased by 12.96% and 18.03% respectively(P<0.05). The gelatinization degree,WSI and WAI were improved after expansion compared with those before expansion of the physical properties. The correlation analysis of the basic nutritional and chemical components and physical properties of ginseng yam blend showed that the gelatinization change rate before and after expansion was significantly negative correlated with the change rate of starch content and amylopectin content(P<0.05),but the change rate of WAI value was significantly positive correlated with IDF(P<0.01),and the change rate of WSI value was significantly negative correlated with the change rate of amylopectin,fat,TDF and IDF content(P<0.05). Total ginsenosides decreased from 5.50% to 5.15% before and after expansion,with significant difference(P<0.05). Conclusion:Through the application of extrusion technology,the physical and chemical properties of ginseng and yam composite powder have been improved,which lays a theoretical foundation for further research.