Using microscopic core plus two-quasiparticle model, the ground-band, β-band, γ-band and partial high spins states at zero temperature in even 148—158 Sm isotopes are successfully reproduced, these values are coincident with recent experimental one. Under canonical ensemble theory, their finite temperature specific heat capacity is calculated. Seeing that the peak of specific heat capacity is the signal of phase transition, it is by means of this approach that the phase transition of model thermo-excited, one from the superfluid nuclear phase to the normal phase, and one from the deformed shape to the spherical shape taken place in nuclei may be described untidily. The aligned energy and the identity of two-quasiparticle are discussed, and then the thermal stability of nuclear shape is investigated.