The invention belongs to a multi-sensor passive positioning technology, and provides a novel method for continuously positioning a scanning system radar radiation source under the condition of an unknown scanning rate. The method comprises the following steps: in the consideration that the scanning rate can be regarded as an unchangeable constant, projecting measured information at all the moments to a target state space to obtain an estimated scanning rate value; then performing recursive optimization in the maximum gradient direction until convergence occurs, and finally calculating maximum likelihood estimation of a target state. The method can effectively estimate the scanning rate of a radiation source target and state information thereof, and the estimation accuracy of a target position is improved.