Abstract: The business cycle synchronization in Chinese six regions was discussed by using techniques in frequency domain with natural logarithm of annual GDP data over period 1952-2004. Several researchers proposed that regional business cycles synchronize due to a nonlinear “phaselocking” process and one can test the necessary condition for phaselock to support the phaselocking hypothesis. According to this theory, empirical evidence to support the necessary conditions for phaselocking in Chinese regional business fluctuations was presented by use of Granger causality tests, Vector autoregressive(VAR) impulse response functions, variance decompositions and tests for nonlinearities. The results suggest that regional business cycle synchronization may be due to a nonlinear phaselocking progress.