The invention relates to an in-situ detection method of melt intrinsic convection fluctuation. The in-situ detection method comprises the steps of: performing Fourier transform processing on an interface phase electrical signal through real-time collection of the interface phase electrical signal between crystal and melt during growth of the crystal, extracting a long-period signal from the processed interface phase electrical signal so as to adopt the extracted long-period signal as a melt intrinsic convection fluctuation signal, and performing acquisition of melt intrinsic convection data according to a fluctuation rule of the melt intrinsic convection fluctuation signal so as to feed back a convection state at a crystal growth interface. The invention further relates to a control methodof the melt intrinsic convection fluctuation, and crystal growth conditions are regulated according to the feedback convection state, so that convection fluctuation at the crystal growth interface iscontrolled. The invention also relates to a control system of the melt intrinsic convection fluctuation, and the control system comprises an electrical signal collecting system, an electrical signalprocessing system and a convection regulating system. Through the in-situ detection method, control method and control system, real-time and accurate feedback of the melt convection fluctuation stateat the crystal growth interface can be achieved, and closed-loop control can be achieved.