The invention provides a sound mixing method and system for a conference system, and the method comprises the steps: responding to the detection of a voice signal of each member, and calculating the voice energy of a voice signal of a voice input end of each member; dividing each member into a first set and a second set based on the voice energy and a preset first threshold value, collecting the members whose voice energy is greater than or equal to the first threshold value into the first set, and collecting the members whose voice energy is less than the first threshold value into the secondset; in response to the fact that the difference value between the maximum value of the voice energy in the second set and the minimum value of the voice energy in the first set is larger than or equal to a preset second threshold value, replacing members of the maximum value of the voice energy in the second set and members of the minimum value of the voice energy in the first set, and updatingthe first set and the second set; and mixing, synthesizing and outputting the voice signals in the first set. On the basis of dynamic grouping, meaningful voice signals are guaranteed to be output, and audio quality is prevented from being affected by excessive noise.