like the tittle, i want direct get pwm's Vrms ,as same as used AC meter to read pwm voltage .
I am assuming you just want to put parts together, you can but it is not a plug and play. I am not sure what type of AC meter you are using to read PWM voltage. Start with this link Waveforms to get a bit of background on how RMS is calculated from a non sonsiduial waveform. Try this link to see how somebody else did it: Interfacing ZMPT101B AC Voltage Sensor Module w/ Arduino
thanks, i try it later