In view of the single invalid data of the optoelectronic deflection meter system in the engineering practice of the bridge structural health monitoring system, which bring the illusive alarm and can not be identified by the traditional methods of signal processing and data analyzing，the paper analyses the characteristics of the single invalid data, and formalizes and describes them. And then, according to the features of the bridge structure changing slowly, a novel filtering algorithm is put forward based on data variety rate to identify the single invalid data, which can distinguish the single invalid data caused by sensors system from by bridge structure，and obtains better application effect for engineering practice.