HOW to set the traveling speed while the drone is traveling between two published position_point in OFFBOARD_MODE

I am flying the drone with mavros by position_point, I am wondering whether it’s possible to decide how fast the drone can fly between two published position_point ?

I’m not sure, but you could try these parameters:
https://dev.px4.io/en/advanced/parameter_reference.html#MPC_XY_CRUISE
https://dev.px4.io/en/advanced/parameter_reference.html#MPC_XY_VEL_MAX