We investigate a corpus of lexical substitution speech errors in Mandarin conversation data and present how Mandarin speakers produce erroneous lexical items and how these items are related to the intended words. The corpus includes 747 lexical speech errors from 100 participants and applies the part-of-speech definition of the Academia Sinica Corpus. Our results partially match with the observations in Germanic and Romance languages. As an example, the data from Mandarin native speakers shows that erroneously produced words and target words are almost always found in the same parts of speech. Moreover, noun substitutions are the most common type of substitution within the majority of content word pairs. However, the occurrence of verb errors is higher in Mandarin than in other languages, possibly reflecting a word frequency effect.