Objective To evaluate the relationship between the optimal length of peripherally inserted central catheter(PICC) fixation,and the height of adult patients and the incidence of mal-position.Methods Totally 200 patients aged above 20 years undergoing PICC were divided into three groups according to height:group A(150-160 cm),group B(161-170 cm) and group C(171-180 cm).The optimal length of PICC fixation and the location of the catheter tip were compared by anteroposterior(AP) chest radiograph.Results The PICC catheter lengths on the left and right arms were significantly differed among the three groups(P0.01).Significant differences were also observed in PICC catheter lengths on the left and right arms within each group(P0.05).The ratio of optimal tip positions of PICC among the three groups had no significant difference(P0.05).There was no significant difference in the ratio of optimal tip positions and mal-positions on the left and right arms in the same group(P0.05).The incidence of mal-positioning was significantly higher in right-side catheters than that in left-side catheters(P0.05).Conclusion The length of the optimal position is related to the height of the patients with PICC.Measures should be taken to prevent PICC mal-position when the intubation of PICC is carried out on the right arm.