  We propose a spin-half approximation method for two-component condensation in
double wells to discuss the quantum entanglement of two components. This
approximation is presented to be valid under stationary tunneling effect for
odd particle number of each component. The evolution of the entanglement is
found to be affected by the particle number both quantitatively and
qualitatively. In detail, the maximal entanglement are shown to be hyperbolic
like with respect to tunneling rate and time. To successively obtain large and
long time sustained entanglement, the particle number should not be large.
