In GNSS era,how to effectively enhance the navigation signal integrity monitoring capacity by using multi-frequency information is becoming a hot topic and the mainstream of RAIM technique.Based on "virtual multi-frequency" ionosphere delay model,the paper proposed a novel virtual multi-frequency integrity monitoring algorithm for the single-frequency receiver,then presented a new pre-whitening technique which was easily implemented in the receiver hardware when the measurement error covariance matrix was not diagonal.The simulation results showed that the "virtual multi-frequency" RAIM technique not only broke through the number limit of visible satellites of traditional RAIM algorithms,but also greatly enhanced the RAIM performance without changing the receiver hardware structure.And the researches of this paper may have a harmonious theoretical significance and practical value to the RAIM technique.