An electrical connector module for mating with a complementary connector module comprises a housing defining a channel formed on a top surface thereof and a mounting slot recessed downwardly from a bottom surface of the channel; a releasing mechanism received into the channel, the releasing mechanism defines a tab extending into the mounting slot, and an actuator formed on a front end thereof; and a resilient piece received into the mounting slot, the resilient piece having a front end abutting against a front inner surface of the mounting slot and a rear end abutting against the tab; the complementary connector module comprises a latching member locked in the front end of the channel and located above the actuator; the releasing mechanism moves forwardly, the actuator extends into a front end of the channel and raises up the latching member along a vertical direction.