Mobile wireless sensor networks(MWSNs)may be under attack due to their large-scale characteristics. One of the main threats is to inject malware into some nodes. To prevent malware from spreading in a largescale MWSN, an effective measure is to immunize susceptible nodes by disseminating and installing security patches. This work suggests a novel modeling framework and some mathematical models based on the pulse differential equation and the epidemic theory, in which the immunization operations are implemented on susceptible nodes in a pulse way. The maximum immunization period of time is derived to minimine the number of immunization operations while ensuring malware extinct over time in the MWSN. The theoretical results are confirmed by extensive simulations. One of the main threats is to inject malware into some nodes. To prevent malware from spreading in a large scale MWSN, an effective measure is to immunize susceptible nodes This work suggests a novel modeling framework and some mathematical models based on the pulse differential equation and the epidemic theory, in which the immunization operations are implemented on susceptible nodes in a pulse way. The maximum immunization period of time is derived to minimine the number of immunization operations while ensuring malware extinct over time in the MWSN. The theoretical results are confirmed by extensive simulations.