The invention discloses a noise decibel-based online fault detection method and system for concrete production equipment. The detection method comprises the following steps of 1, acquiring parameter information of noise decibels of concrete production equipment at different operation points in real time; 2, after the concrete production equipment is operated for a period of time, respectively calculating a parameter average value of the noise decibels in the period of operation time; 3, comparing the parameter information of the noise decibels acquired in real time with the average value calculated in the step 2 to judge whether the parameters have abnormal information or not; and 4, judging fault points of the concrete production equipment according to the abnormal information. The methodand system are capable of monitoring the operation condition of the concrete production equipment in real time, automatically recognizing the potential fault factors at corresponding working points of the equipment and analyzing the potential fault phenomena, so as to solve the generation of environment pollution factors due to equipment faults and ensure that the mixing plants accord with the related requirements of environment quality in the production process.