to suit their needs and desires when users want more standby time they can choose an assembly without the display module 20 for reducing battery power consumption in case the display module 20 is damaged users may buy another display module 20 at a lower cost for replacement without the need to buy a whole new set of the mobile phone at a higher price referring to fig4 for another embodiment of this invention for increasing the standby time an extra rechargeable battery 30 a may be added to the display module 20 for supplying power needed in the display module 20 then the standby time of the communication module 10 may be increased 0022 fig5 illustrates yet another embodiment in which the display module 20 includes a sonic input unit 23 engaged to the second connection port 22 when the communication module 10 is coupled with the display module 20 the total mobile phone set has a greater length hence user may hear the incoming voice from the sonic output unit 14 at the communication module 10 and speak to the sonic input unit 23 at the display module 20 at more focused distances to the ear and mouth thereby to make communication more effective and comfortable as the modular mobile communication device of this invention adapts a detachable design and construction the communication module 10 may also be coupled with.