Aim To study the influence of initial concentration change of reactant on conversion ratio. Methods According to chemical equilibrum principle and the use of derivative in judging the increasing and decreasing of function. this influence has been discussed. Results The rule of the influence has been deduced while initial concentration of other reactants is constant in the chemical reactions in which one or two or three species of reactants may be contained. In addition

the rule of the influence has also been deduced while initial concentration ratio of reactants is equal to their coefficient ratio. Conclusion The deduced results are instructively important for analysing chemical reactions and chemical processes.