Abstract: The buildup and principle of proportioning system in rolling reconstituted tobacco processing line were introduced.The factors causing the fluctuation of mixture moisture content, including the errors of powder and liquid feeding, weighing and the variation of powder moisture content, were analyzed.Meanwhile, the method of compensation for feeding error and fluctuation of powder moisture content, and software setting of the system were given. The stabilization of mixture moisture content after proportioning was ensured by the compensation for error.