In order to analysis the electromagnetic coupling of field-to-line in a reverberation chamber, a multi-group plane-wave algorithm is proposed to simulate the electromagnetic field, which is considered to be the same field distributions as a real chamber within the test volume. The results derived by this algorithm for field-to-line coupling are very well agreed with the experiments and so verified the effectiveness of this algorithm. By using this method, the computer calculation time can be significantly reduced. Especially, this is very useful for high frequency field simulation in a reverberation chamber.