Quantum thermal entanglement of two next nearest-neighbor qubits in a four-qubit isotropic Heisenberg XY model consisting of spin 1/2 and spin S in a homogeneous external magnetic field B was investigated by concurrence measure of entanglement. The results show that the external magnetic field can induce the thermal entanglement of two next nearest-neighbor qubits. The amplitude of thermal entanglement is dependent on the spin S,temperature T and homogeneous external magnetic field B. As a result,it is feasible to control thermal entanglement by adjusting the value of external magnetic field B. When S is sufficiently large,the threshold temperature above which there is no thermal entanglement may also be very high. The feature can be used in high-temperature entanglement of condensed matter systems and it will be useful in the research of quantum information in solid systems.