Abstract: The growth rule of root system of winter wheat in semiarid red clay soil hills in west Henan was investigated during 1987～1993. The results show as follows: the growth of primary and secondary roots and root number tended to increase with prolongation of the growing of root system, the maximum depth of the root system can be 340 cm, the increasing equation of root biomass (Y, kg·mu-1) is Y=33.013-2.732X+0.0902X2-0.000999X3+0.00000466X4- 0.00000000770X5, which has two peaks before overwintering and duration from rising to jointing respectively. The distributions of the root number and biomass inside soil were in keeping with the equation Y= ae-bx. When soil water capacity was bigger than 16 %, the growth of root system and aboveground part was all abnormal. The function relationship between root depth and soil water capacity around root tips can be described with equation Y= 2.009e0.2204X. Appearing of secondary root was not corresponding with number of leaves on the stem but with tillering. The dry matter accumulation of root system was in coordination with aboveground part. The increasing of primary root number can improve ear/plant. The increasing of secondary root number can raise grain/ear and weight/1000 grain. The improvement of root growth and yield due to soaking seed with microelement fertilizer or hormore was significant.