The invention provides a user privacy protecting method and system. The method comprises the following steps: according to a data request sent by a current demand side, inquiring the corresponding data of a current user as first data; according to the data request, inquiring a data record sent to the current demand side, and based on the data record, acquiring all data sent to the current demand side and related to the current user as second data; searching the number of the users with the first data and the second data in all data sent to the current demand side, judging whether the number of the users is less than the preset number or not, if yes, conducting generalization processing on the first data, taking the processed data as the first data and executing the step again, and if no, conducting weak generalization processing on the first data, and sending the first data subjected to weak generalization processing to the current demand side, wherein the preset number is an integer which is greater than or equal to 2. According to the user privacy protecting method and system, valuable data can be provided for the demand side to the maximum extent on the premise of protecting user privacy.