A method for realizing a virtual SIM card, characterized by comprising: when a mobile terminal requests to access a communication network, connecting to a cloud service terminal through a wireless network; after the mobile terminal receives an authentication request sent by the communication network, requesting the cloud service terminal to perform authentication calculation and feeding an authentication result obtained by the authentication calculation back to the mobile terminal; and sending, by the mobile terminal, the received authentication result to the communication network; wherein, connecting to the cloud service terminal through the wireless network comprises: the cloud service terminal verifying the validity of the mobile terminal, wherein if the verification is passed, a normal connection is performed, otherwise, the mobile terminal is not allowed to access the cloud service terminal; wherein, the validity verification comprises: when the mobile terminal sends a new value, obtained by calculating a preset user name and a preset password that are used when the mobile terminal connects to the cloud service terminal according to a predefined algorithm, to the cloud service terminal through the wireless network, the cloud service terminal decrypting the received new value adopting the same predefined algorithm, and comparing the user name and the password decrypted with a user name and a password prestored by the cloud service terminal corresponding to the mobile terminal, wherein if the comparison result is that the user name and the password decrypted are the same as the user name and the password prestored, the verification is passed. when a mobile terminal requests to access a communication network, connecting to a cloud service terminal through a wireless network; after the mobile terminal receives an authentication request sent by the communication network, requesting the cloud service terminal to perform authentication calculation and feeding an authentication result obtained by the authentication calculation back to the mobile terminal; and sending, by the mobile terminal, the received authentication result to the communication network; wherein, connecting to the cloud service terminal through the wireless network comprises: the cloud service terminal verifying the validity of the mobile terminal, wherein if the verification is passed, a normal connection is performed, otherwise, the mobile terminal is not allowed to access the cloud service terminal; wherein, the validity verification comprises: when the mobile terminal sends a new value, obtained by calculating a preset user name and a preset password that are used when the mobile terminal connects to the cloud service terminal according to a predefined algorithm, to the cloud service terminal through the wireless network, the cloud service terminal decrypting the received new value adopting the same predefined algorithm, and comparing the user name and the password decrypted with a user name and a password prestored by the cloud service terminal corresponding to the mobile terminal, wherein if the comparison result is that the user name and the password decrypted are the same as the user name and the password prestored, the verification is passed.