Based on the Y-shaped cavity orthogonal polarized dual-frequency helium-neon laser, the influences of pump current, operating point as well as the loss of resonator on the locking-threshold frequency difference are analyzed according to Lamb′s semi-classical theory. In order to measure the minimum frequency difference of the Y-shaped cavity orthogonal polarized dual-frequency helium-neon laser, an experimental system is set. Various factors, especially pump current and operating point, are studied in the experiment for the first time. The results show that either the pump current increasing or operating point approaching the gain curve center can cause the minimum frequency difference to decrease. When the pump current value is greater than 2.2 mA with its working state at the optimal operating point, the locking-threshold frequency difference can be less than several MHz.