We can connect only two serial interface with Arduino uno v3 (first to Tx,Rx and second to Software Serial) but can not connect more than two 2 serial interface with Arduino uno v3.
Is it possible to connect two serial interface to Arduino uno v3 through MUX (without using Tx,Rx) using Software Serial?
but can not connect more than two 2 serial interface with Arduino uno v3.
That might not be correct. Just how are you planning to use the serial interface?
You can always use an I2C UART if you want more serial ports. Using a mux does not work with serial data as you are leaving the other channel alone for half the time and you will miss something.
As zoomkat says, depending on how you intend to use them, you might be able to use two software serial ports as well as the hardware port.
Take a look at the IDE's "SoftwareSerial" "TwoPortReceive.ino" example
