The rock physical characteristics and gravity and magnetic anomaly in Taiwan strait and neighboring area has been studied in this paper. Under the restrictions of deep seismic data gravity anomalies of two profiles across central and south part of Taiwan island are calculated. The results show that the model of crust thicken across central part of Taiwan island accords with the data of geophysical prospecting, resulting from collision between Eurasia plan and Philippine blocks. The density distribution of crust in southern Taiwan has been showed, during South China Sea block nosing down Philippine block.