The study aim to explore the quality effects of inner and outer water bodies at Tram Chim National Park. Water samples from inner canals and outside cultivation areas of Tram Chim National Park were collected in dry and rainy seasons for water quality recorded. Then the water quality index calculated from water quality parameters based on the VN_WQI guideline of the Vietnam Environment Administration. The VN_WQI values shows that the water quality in the canal system inside the park is good and can be used for irrigation or navigation; but the water quality at surrounding cultivation areas of the park indicated the heavy pollution that needs to be addressed. It could be seen that the polluted water sources from outside could affected the quality of water bodies inside the park, more specifically in dry season when water pumping from outside canals to inner canal to maintain water level. Based on the fact, some key solutions were suggested to protect the water bodies and the rich biodiversity in the national park.