The study uses a pre-test, post-test experimental randomised control group design to examine the effects of a blended learning environment on Chinese adult learners' English acquisition. At the initial stage the study constructed a blended learning environment composed of three parts: task-based online learning, group-based peer learning and class-based traditional learning. Then the study chose two classes with no significant difference in their English abilities as experimental class (EC) and control class (CC) randomly. During the following term one teacher taught the EC and the CC with a blended learning environment or a traditional learning environment, respectively. At the end of the term, the study examined the learners' English abilities in the aforementioned classes. This study found that learners in EC significantly outperformed those in CC, especially in English writing abilities. The findings indicate that a blended learning environment can improve Chinese adult learners' English acquisition, especially their practical English abilities.