Objective To study the different effects from different concentration ratios of polymorphonuclear neutrophil (PMN) to tumor cell (TC) on the process of tumor cell adhesion to endothelial cell (EC) in shear flow. Methods PMNs and TCs with different concentration ratios (PMN-TC ratio) were added into the parallel plate flow chamber, and changes in the numbers of transient and accumulative adhered TCs on ECs at different shear rates (50 s-1，100 s-1，200 s-1) were analyzed. Results The transient and accumulative adhesion of TCs on ECs at PMN-TC ratio of 3︰1 significantly increased as compared to that at PMN-TC ratio of 1︰1, especially under high shear flow condition (100 s-1 and 200 s-1). Moreover, in the 5 minute-observation period, the effect of PMN-TC ratio on TC adhered to ECs occurred earlier when the shear rate increased. Conclusions The increase of PMN-TC concentration ratio can promote TC adhesion to ECs in shear flow, and the research findings provide significant references for studying TC metastasis in blood vessels and the target therapy of tumors.