Dynamic mechanical analysis (DMA) tests are conducted on styrene-based shape memory polymer(SMP) to investigate its glass transition behaviors. The tensile tests at various temperatures are operated to detect the stress-strain relationship of styrene-based SMP. The material elastic moduli and yielding limits at 25oC, 30oC, 40oC, and 50oC are determined according to the results of tensile test. A new material parameter function is supposed to express the glass transition behavior of styrene-based SMP. The shape memory thermo-mechanical cycle of styrene-based SMP is numerically simulated by Tobushi’s constitutive equation coupled with the new material parameter function. Numerical results show the new material parameter function can express the thermo-mechanical properties of styrene-based SMP effectively.