The invention discloses a multivariate time lag controlling method used in combustion process of a coal-fired unit or an industrial boiler, which is characterized in that the method comprises the following steps: building a mathematical model of the combustion process via a modeling software, determining a time lag compensator according to the mathematical model of combustion process G(s), designing a pre-compensator Kp(s) and a master controller Kc(s), constructing OPC communication between a control device computer and an operating station to realize information exchange between the control device and a DCS system or a PLC system, and receiving set values and actual values of flue gas oxygen content and vapor pressure of the DCS system or the PLC system during the combustion process or directly collecting the actual values of the flue gas oxygen content and the vapor pressure during the combustion process via the control device computer. The multivariate time lag controlling method fulfills the dynamic characteristics of the combustion process and elaborately designs the controller with computer-aided design and simulation method, so that the control system is stable, and the vapor pressure is controlled within a range stipulated by the process. The method realizes automatic adjustment of air-coal ratio, improves boiler thermal efficiency, and reduces coal consumption.