Adverbial phrase (AdP) contains rich and indispensable information, however, translating them properly is one of big challenges for machine translation (MT) systems. In this paper, we systematically present a contrastive analysis of MT of AdPs from Chinese to Portuguese. Our study is conducted on The International Chinese Newsweekly corpus which consists of 46 Chinese texts (ST) with their respective Portuguese translations given by a state-of-the-art Portuguese–Chinese MT system and human beings (HT). By comparing the syntactic structures of these texts in ST, PCT, and HT sides, we found that nearly 90 % MT outputs suffer structural inconsistency with poor translation qualities. Therefore, we discuss and finally propose a series of grammar rules to address the problem. We believe that this work could inspire both MT researchers and industries to boost the performance of Portuguese–Chinese MT systems.