Northeast mung bean (Phaseolus radiatus) as materials were used to study development characteristics of border cells by suspended culture with agar pour plate.The results showed that bean border cells were spherical shape with early development,and develop into oval shape,long oval shape and strip shape with growth gradually.The root border cells have high viability in development process and the viability were at 70%~80% and tended to be stable when the root length was greater than 10 mm;The number of root border cells reached maximum (about 13 000)when the root length was 25~30 mm;Pectin methylesterase activity of root cap reached the highest value（1.486 H⁺μmol·root cap^-1·h^-1） with 5 mm root length,then changed in 1.107~1.256 H⁺μmol·root cap^-1·h^-1 and tended to be stable with the root elongation.