Stress is one of the key suprasegmentals in English sound system. It plays an important role in intelligibility and comprehensibility. However, stress often poses problems for Chinese EFL Learners. Chinese learners of English often misplace the stress in English words and sentences which subsequently may interrupt the flow of communication and lead to unintelligibility. Therefore, the correct placement of stress is a main concern in EFL speech intelligibility and training, and it is particularly important for Chinese learners of English because they have a drastically different stress system in their native language. There is evidence to suggest that the transfer of native language sound systems is one of the major reasons for foreign language pronunciation errors. This paper examines the differences between Chinese and English stress. Based on such contrastive analysis of English and Chinese stress, experiments are conducted to investigate the reasons for Chinese EFL learners' pronunciation difficulties in English stress, and finally implications for English pronunciation teaching are drawn.