  A formula to evaluate the entanglement in an one-dimensional ferrimagnetic
system is derived. Based on the formula, we find that the thermal entanglement
in a small size spin-1/2 and spin-s ferrimagnetic chain is rather robust
against temperature, and the threshold temperature may be arbitrarily high when
s is sufficiently large. This intriguing result answers unambiguously a
fundamental question: ``can entanglement and quantum behavior in physical
systems survive at arbitrary high temperatures?"
