A two-stage regulation and control method and system for plasma density belongs to the technical field of plasma diagnostic research, and solves the problem that the current gas discharge type plasmadensity is inaccurate, unstable, and untimely by the conventional single variable density control method. The method of the present invention is: when the deviation D between the actual density [rho]of the plasma and the preset density [rho]T satisfies the condition of |D|>60%[rho]T, a piezoelectric crystal valve is first used to control the amount of intake air to coarsely adjust the plasma density; and when the deviation D between the actual density [rho] of the plasma and the preset density [rho]T satisfies the condition of 20%[rho]T <= |D| <= 60% [rho]T, the plasma density is finely adjusted by adjusting the power of a RF power source until the condition of |D|<[epsilon] is satisfied, wherein [epsilon] is the allowable error.