The invention discloses a detector drive mechanism in a petroleum well. The detector drive mechanism in the petroleum well comprises a drive motor and a speed reducer. Gear sets and an output shaft are arranged in the speed reducer. Inner teeth are arranged on the inner surface of a shell of the speed reducer. All the gear sets except the last gear set are each provided with a sun gear. Each gear set comprises a gear disc, one face of each gear disc is provided with three planet gears, the center of the other face of each gear disc is fixedly provided with the corresponding sun gear, on the one hand, every three planet gears are meshed with the inner teeth, on the other hand, every three planet gears are meshed with the corresponding sun gear of the previous level, and therefore the gears are connected level by level. The drive motor supplies original power to a high-temperature drive mechanism, rotation of the drive motor is transmitted to the output shaft through the speed reducer, and meanwhile the rotation moment is increased. Heat exchange conducted between the external environment and the drive mechanism is stopped through a heat insulation layer and it is guaranteed that the detector drive mechanism works stably at the high temperature. The application temperature of the drive mechanism ranges from -40 DEG C to 200 DEG C and the drive mechanism can work stably at the high temperature of 150 DEG C for over 15 minutes.