Abstract: In order to understand correlation and relations of primary and secondary on characters which influencing yield and quality of sweet potato, multiple statistic methods were used to analyze relationship of correlation and principal component analysis on agronomic traits and quality traits in regional trails of North China. Results showed that starch yield was significant positive related with percentage of dry matter and percentage of starch, dry matter yield was also the same relationship with diameter of stem and percentage of big and middle tuberous roots, but fresh yield only was significant positive related with percentage of big and middle tuberous roots. By principal component analysis, we found that percentage of big and middle tuberous roots, diameter of stem and resistance index of black pot consisted of the highest contribution principal component for starch yield and dry matter yield, and the rate of contribution of first principal component are respectively 29.67% and 30.13%. But percentage of big and middle tuberous roots and disease index of root pot was the biggest effect principal component for fresh yield, and the rate of contribution of first principal component is 30.71%. And extremely negative correlation relationship was indicated between starch content and reducing sugar content, soluble sugar content, sweetness. But crude protein content was weak negative related with reducing sugar and soluble sugar content. Principal component of quality traits showed that reducing sugar content, soluble sugar content and sweetness after stewing mainly contribute to quality of sweet potato, and the rate of contribution of first principal component is 59.12%. The second principal component includes crude protein content and viscosity after stewing, and the rate of contribution of first principal component is 23.75%. It was concluded that different emphasis of agronomic traits affects the formation of different yield goal, sweetness and waxy are mainly traits which influencing quality traits of sweet potato.