In this study, novel Pt-IrO2 nanofiber catalysts for oxygen evolution reaction (OER) were successfully prepared using the electrospinning method with a high-concentration precursor solution. The composition and structure of catalysts were characterized, and the electrocatalytic performance of the nanofiber catalysts in water electrolysis was investigated from various aspects such as overpotential, charge transfer resistance, and exchange current density. Special attention was paid on the effect of Pt/Ir ratio on the electrocatalytic activity of the electrospun nanofibers. The results showed that the Pt-IrO2 nanofiber catalysts with average fiber diameters ranging from 10 to 100 nm can be successfully obtained by the electrospinning method, and the average diameter decreased with the increase of Pt content. Since a bigger amount of IrO2 content and a thinner fiber structure are all beneficial to the electrocatalytic performance, the Pt-IrO2 catalysts with Pt:Ir = 1:9 and Pt:Ir = 9:1 both showed better catalytic performance for OER than the commercial IrO2, which was also demonstrated by the lower charge transfer resistance and higher exchange current density. As a result, the overpotentials of Pt-IrO2 catalysts with Pt:Ir = 1:9 and Pt:Ir = 9:1 are 50 mV and 32 mV lower than the overpotential of the commercial IrO2 at 30 mA cm(-2) in 0.5 M H2SO4, respectively. The electrospun Pt-IrO2 nanofiber catalyst with proper Pt content seems to be very promising since it can not only improve the catalytic performance and the safety of PEM electrolysis cells, but also reduce the amount of more expensive Ir in catalysts.