Objective To study hemodynamics in 3D microvascular networks and interstitium of solid tumor by numerical method. Methods Generate 3D vascular networks of solid tumor numerically; calculate intravascular pressure、interstitial pressure and velocity by Poiseuille's law and Darcy's law, respectively. Results To vessels outside tumor, blood pressure drops rapidly, but to vessels inside tumor, it changes a little which could be assumed constant; interstitial pressure of tumor is high and plain in the center region and drops rapidly in the edge, which is reverse for interstitial fluid velocity. Conclusion An effective 3D vascular networks inside and outside of tumor was obtained; the results of hemodynamics consist with basic physiological features, and provide a credible model and method for research about drug delivery in tumor.