The sequence structure and crystallization behavior of the ethylene oxide-tetrahydrofuran random copolymer, P(E-co-T), were investigated by the quantitative ¹³C-NMR spectra, WAXD, and DSC. The thermostat polyurethane elastomers were prepared with P(E-co-T) copolyether, and the network structure and mechanical properties of the resultant polyurethane elastomers were studied. Based on the quantitative ¹³C-NMR, the existence of the micro-blocks ［THF］_n(n≥3) in P(E-co-T) chains was determined, and the content of ［THF］_n in P(E-co-T) copolyethers was calculated. The WAXD and non-isothermal DSC results of the P(E-co-T) copolyether reveal that the crystalline formed by the THF units is observed at -40 ℃, and the dependence of the molecular weight on crystallization capability for the P(E-co-T) copolyether was closely related to the content of the micro-blocks ［THF］_n in P(E-co-T) chains. The results of the mechanical properties of the polyether polyurethane elastomers reveal that the tensile stress decreases and strain at break increases with molecular weight of the prepolymer, while an opposite trend is obtained at -40 ℃ for the polyether polyurethane elastomers, which is caused by the different crystallization capability at -40 ℃.