Probing the dynamical behavior of dark energy We investigate dynamical behavior of the equation of state of dark energy w$_{de}$ by employing the linear-spline method in the region of low redshifts from observational data (SnIa, BAO, CMB and 12 H ( z ) data). The redshift is binned and w$_{de}$ is approximated by a linear expansion of redshift in each bin. We leave the divided points of redshift bins as free parameters of the model, the best-fitted values of divided points will represent the turning positions of w$_{de}$ where w$_{de}$ changes its evolving direction significantly (if there exist such turnings in our considered region). These turning points are natural divided points of redshift bins, and w$_{de}$ between two nearby divided points can be well approximated by a linear expansion of redshift. We find two turning points of w$_{de}$ in z ∈ (0 , 1 . 8) and one turning point in z ∈ (0 , 0 . 9), and w$_{de}$ ( z ) could be oscillating around w = − 1. Moreover, we find that there is a 2 σ deviation of w$_{de}$ from − 1 around z = 0 . 9 in both correlated and uncorrelated estimates. $^{∗}$Electronic address: cairg@itp.ac.cn $^{†}$Electronic address: sqp@itp.ac.cn $^{‡}$Electronic address: hbzhang@itp.ac.cn 1 arXiv:1001.2207v2 [astro-ph.CO] 13 Apr 2010 Abstract Rong-Gen Cai, ∗ Qiping Su, † and Hong-Bo Zhang ‡ Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190, China