The invention discloses a linear dimming method based on a microprocessor. The linear dimming method comprises a rectification portion, a zero-cross detection portion, a control portion, a controlled portion and a load portion. The rectification portion is used for rectifying commercial power into forward power; the zero-cross detection portion is used for detecting the zero crossing point of an alternating current; the control portion carries out timing after detecting a zero crossing signal and outputting a signal to control the controlled portion to enable the load portion to be controlled to work; the control portion adopts the microprocessor MCU for controlling; and the controlled portion adopts a silicon controlled rectifier. According to the two-line linear LED lamp dimming control method, the microprocessor MCU judges the work frequency of the alternating current, and calculates the time of the zero crossing point by detecting the AC input voltage phase angle, and thus on/off state of LEDs in the corresponding sections can be controlled.