The invention relates to an electro-hydraulic control device of an excavating machine and a flow control method of a load-sensing variable pump, and the electro-hydraulic control device of the excavating machine comprises a pressure sensor, a hydraulic oil tank, an executing mechanism and an executing mechanism, wherein the pressure sensor is connected with the executing mechanism and the executing mechanism respectively through a load-sensing control oil passage, the executing mechanism and the executing mechanism are connected with the hydraulic oil tank through the load-sensing control oil passage, the hydraulic oil tank is connected with the load-sensing variable pump through the load-sensing control oil passage and the load-sensing variable pump is connected with the pressure sensor through the load-sensing control oil passage. The invention further comprises a method for flow control of the load-sensing variable pump by utilizing the electro-hydraulic control device of the excavating machine. By adopting the device in the invention, a plurality of constant-power control curves of the load-sensing variable pump without a mechanical constant-power control mechanism can be simulated for meeting the requirements of enabling the power of a hydraulic system to be matched with the power of an engine, thereby enabling the hydraulic system to be always in the optimal economic working conditions and reducing energy consumption.