The invention relates to the field of robot trajectory planning, and provides a smooth transition method of multi-space trajectory planning of a teaching robot, aiming at solving the unsmooth problemin the trajectory switching process. The smooth transition method comprises the steps that a teaching program of the teaching robot is analyzed, the switching direction of the trajectory planning is judged, if the trajectory planning is that the switching direction is from cartesian space to joint space, a tail end of cartesian space trajectory planning is acquired, according to the requirements on a path and a velocity, a first posture and a first velocity at the tail end are acquired, first angular velocities of various joints are obtained by employing a jacobi matrix, and by taking an angleindicated by the first posture as a starting angle and the first angular velocities as starting velocities, joint space trajectory planning is carried out; or else, a starting point of the cartesianspace trajectory planning is acquired, a second posture at the starting point and second angular velocities of the various joints are obtained, and by taking an angle indicated by the second posture as a terminal angle and the second angular velocities as terminal velocities, the joint space trajectory planning is carried out. Smooth transition of the trajectory planning in space switching is realized.