The invention discloses a mobile phone charge calculating device, which is characterized by comprising a wireless network, a service support server (9), a mobile phone, a network synchronization module (1), a monitoring module (2), a pricing module (3) and a storage module (4), wherein the network synchronization module (1) is arranged on the mobile phone and is used for synchronizing a charge billing rule of a user to the mobile phone; the monitoring module (2) is used for recording user conversation details; the pricing module (3) is used for pricing the user conversation details recorded by the monitoring module (2) by using the charge billing rule on the network synchronization module (1); and the storage module (4) is used for storing a bill after pricing in the mobile phone. The calculating device has high real-time performance and accuracy during charge calculation, can query the charge on the mobile phone directly, has a small charge detail record data volume, needs no password and is more convenient and efficient, and simultaneously the stored bill is convenient for a user to check the charge.