[en] The non-linear coupling due to the beam-beam interaction with crossing angle has been studied. The major effect of a small (∼12mrad) crossing angle is to excite 5Q_x±Q_s=integer coupling resonance family on large amplitude particles, which results in bad lifetime. On the CESR, a small crossing angle (∼2.4mr) was created at the IP and a reasonable beam-beam tune-shift was achieved. The decay rate of the beam is measured as a function of horizontal tune with and without crossing angle. The theoretical analysis, simulation and experimental measurements have a good agreement. The resonance strength as a function of crossing angle is also measured