The present invention discloses a method for separating pentene-1 and pentene-2 from C5 by-production distillates. According to the present invention, the by-production distillates being subjected to diolefin and isopentene removing during a C5 separation process are adopted as raw materials, and azeotropic rectification, simple rectification, isomerization and other process methods are used to obtain the high-purity pentene-1 and the high-purity pentene-2; the technical defects of complex process and high energy consumption in the separation of pentene-1 and pentene-2 from C5 by-production distillates in the prior are solved with the method of the present invention; and with the application of the method to separate the pentene-1 and the pentene-2 from the C5 distillates, the characteristics of high purification precision, stable product quality, low energy consumption, stable operation and easy industrial production are provided.