The invention discloses a real-time tumor site monitoring system and a real-time tumor site monitoring method. The real-time tumor site monitoring system comprises a pneumotachometer, a machine head MLC driving mechanism and a PLC (programmable logic controller). The pneumotachometer comprises a pneumotachometer body (1), a trumpet tube (4) and a gas outlet tube (5) are arranged on the left and right sides of the pneumotachometer body (1), a flowmeter (6) is arranged on the gas outlet tube (5), a first open-close door (7) is hinged to the end of the gas outlet tube (5), the machine head MLC driving mechanism comprises two longitudinal guide rails (10), two sliders (11) sliding along the longitudinal guide rails (10) are arranged on the longitudinal guide rails (10), guide sleeves (12) are arranged on the sliders (11), two horizontal guide rails (17) are arranged between the two opposite guide sleeves (12), and an MLC (13) is arranged between the two horizontal guide rails (17). The real-time tumor site monitoring system and the real-time tumor site monitoring method have the advantages that tumor movement caused by breathing movement can be tracked more precisely and favorable conditions can be offered for subsequent tumor treatment, and the method is simple.