Chinese Pinyin input method is very important for Chinese language information processing. Users may make errors when they are typing in Chinese words. In this paper, we are concerned with the reasons that cause the errors. Inspired by the observation that pressing backspace is one of the most common user behaviors to modify the errors, we collect 54,309,334 error-correction pairs from a real-world data set that contains 2,277,786 users via backspace operations. In addition, we present a comparative analysis of the data to achieve a better understanding of users' input behaviors. Comparisons with English typos suggest that some language-specific properties result in a part of Chinese input errors.