Objective To investigate the peripherally inserted central catheter (PICC) to improve the accuracy of three valve PICC head end position of the fortune with endocardial mapping method.Methods 204 patients with PICC were randomly divided into observation group and control group according to the digital table,102 cases in each group.The observation group used saline infusion method by three valve PICC guided endocardial mapping catheter tip location.The control group received conventional positioning surface positioning method.The accurate rate of end position of the two groups was compared.Results The head position accuracy of the observation group was significantly higher than that of the control group (100.00% vs.93.14%,x2 =3.003,P =0.004).Conclusion The use of saline drip instillation to guide intracardiac electrogram during PICC catheter placement can reduce ectopia and improve the accuracy of the head end position of the catheter,and it is worthy of promotion.