Aiming at the problem that Big data anomaly detection process is easily interfered by edge data， which leads to poor accuracy of Big data anomaly detection， a big data anomaly detection model based on Random forest algorithm was proposed. Firstly， the improved k-means algorithm was used to cluster the big data， and the principal component analysis method was used to extract the features of the big data. Then a big data anomaly detection model based on random forest classifier was built， the extracted features was inputted into the model， a decision tree was built， and the classification accuracy of the classifier was improved by dynamically updating the weight value of the decision tree. Finally， the classification results are output to complete the anomaly detection of big data. The experimental results show that the detection time of the proposed model is about 25 s， the average big data anomaly detection accuracy is 91%， and the false alarm rate is 4.5%.