A modular distributed control LED display system, comprising several LED display module units which are spliced together to form an integrated LED display screen, each of the LED display module units comprises a lamp board and an independent controller, wherein the lamp board is provided with a number of LED light sources, and the independent controller is provided on the back of the lamp board, the independent controller is used to control the working state and display mode of the LED light sources, the independent controller is provided with an independent power module and an independent control module, the independent controller is provided with an input jack and an output jack, the input jack is detachably plugged with an input connecting cable, and the output jack is detachably plugged with an output cable, when several LED display module units are spliced together to form the integrated LED display screen, the input connecting cable and the output connecting cable are connected between any two adjacent LED display module units, wherein each of the LED display module units is detachably assembled in a splicing frame, a number of the splices frames are connected to each other, so that the LED display module units are spliced together to form the integrated LED display screen, the LED display module unit being assemblable in the splicing frame from the front, and being also assemblable in the splicing frame from the back, wherein each of the LED display module units is provided with a connecting lock which is positioned between the LED display module unit and the splicing frame, wherein, when the connecting lock is opened, the LED display module unit is removable from the splicing frame, wherein, when the connecting lock is locked, the LED display module unit is locked in the splicing frame by the connecting lock, the connecting lock comprising a rear opening structure and a front opening structure, wherein the rear opening structure is arranged on the back of the lamp board, and the front opening structure is arranged in the front of the board, the user being able to open the connection lock from the back of the lamp board through the rear opening structure, and at the same time, the user being also able to open the connection lock from the front of the lamp board through the front opening structure, characterised in that the connecting lock comprises a rotating shaft and a locking structure, the locking structure being fixedly connected to the rotating shaft, and rotatable synchronously with the rotating shaft, the rear opening structure being arranged at the rear end of the rotating shaft, and the front opening structure being arranged at the front end of the rotating shaft, wherein, when in use, the user is able to manually turn the rotary button to make the locking structure and the rotating shaft rotate synchronously, so as to open or lock the connecting lock, wherein, when the locking structure rotates and is stuck on the splicing frame, the LED display module unit is assemblable in the splicing frame, wherein similarly, the user is able to insert the front opening tool into the front opening structure and rotate it, thus making the locking structure and the rotating shaft rotate synchronously, so as to open or lock the connecting lock.