how many software serial can Arduino mega 2560 used?

how many software serial can Arduino mega 2560 used?

Same as any other AVR micro - as many as you want, but only one can receive or transmit at a given time. You know that the Mega has 4 hardware serial ports which are not limited by that restriction right?

yes i know that there are 4 hardware serial ports. but i am asking the SoftwareSerial

i used only used

SoftwareSerial mySerial(10, 11); // RX, TX

i want to know all pin that ca used in SoftwareSerial

because i just couldnt understand this one.

The library has the following known limitations: If using multiple software serial ports, only one can receive data at a time. Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69). Not all pins on the Leonardo and Micro support change interrupts, so only the following can be used for RX: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI). On Arduino or Genuino 101 the current maximum RX speed is 57600bps On Arduino or Genuino 101 RX doesn't work on Pin 13

You just posted a list of the pins that can be used for SoftwareSerial, through the miracle of RTFM. If I'm not mistaken, you've answered your own question.