Abstract: Continuous constant thrust is very important in orbital maneuver and escape flight.Small thrust maneuvers are fit for spacecraft rendezvous,and the tangential(or transverse) thrust and radial high-thrust can be applied in escaping from the earth's gravitational field.By using the motion equations of constant thrust maneuver,there is no limit on the thrust-level and no restraints on the relative distance when used in spacecraft rendezvous.Radius and orbital velocities can be directly expressed as functions of time or polar angle,which is helpful for designing flight mission and motion trajectory.Especially,when the initial orbit is circular,for small thrust and short flight time,approximate analytic solutions can be derived from non-dimension form of the motion equations.