The purpose of this study is 1) to identify the changes which the aspectual system of the Shanghai dialect experienced since the modern era and 2) to describe the factors of these changes in terms of language contact. It is known that grammatical markers change slowly and also that Chinese aspect markers contain distinctive characteristics of each dialect. However, in the case of Shanghai dialect, it was confirmed that the changes in the aspect markers occurred at a very high speed. Especially, the forms and the usage which the young people in their 20s and 30s use is very much similar to those of Putonghua. This study argues that the phenomenon is a reuslt of changes in the composition of language population. Since the number of Putonghua users occupies the largest portion of the language population in Shanghai, the language contact between Putonghua and Shanghai dialect will continue to increase. Therefore, it is expected that the dialect levelling of the aspect markers in Shanghai dialect to Putonghua will proceed more rapidly.