Nowadays, big data systems are being widely adopted by many domains for offering effective data solutions, such as manufacturing, healthcare, education, and media. Big data systems produce tons of unstructured logs that contain buried valuable information. However, it is a daunting task to manually unearth the information and detect system anomalies. A few automatic methods have been developed, where the cutting-edge machine learning technique is one of the most promising ways. In this paper, we propose a novel approach for anomaly detection from big data system logs by leveraging Convolutional Neural Networks (CNN). Different from other existing statistical methods or traditional rule-based machine learning approaches, our CNN-based model can automatically learn event relationships in system logs and detect anomaly with high accuracy. Our deep neural network consists of logkey2vec embeddings, three 1D convolutional layers, dropout layer, and max-pooling. According to our experiment, our CNN-based approach has better accuracy(reaches to 99%) compared to other approaches using Long Short term memory (LSTM) and Multilayer Perceptron (MLP) on detecting anomaly in Hadoop Distributed File System (HDFS) logs.