Hi Dear All

Im new comer here ,I want to make a circuit that can adjust stepped down 12VAC(0-12v) like DC circuit by using LM317..I dont want to use variac or transformer secondary taping points with rotary switch..Plz note I'm using step down transformer for getting 12vac from main with 1 or 0.5Amp current..

Thanking you All in Anticipation...

LM317 only works on DC.

One way to get the AC voltage you want is to add a wire wound resistor. The voltage you get will not be accurate and it will vary according to the current you draw.

But, for instance, if you are drawing 1amp, put a 3R3 5watt wire wound resistor in one line and measure the voltage.
If it is too low, put a 10R across the 3R3.

Alternatively you can put a wire wound pot (called a rheostat) in one line and adjust the voltage. (These are expensive and you will need a 10 watt version.)

The other method is to put a number of 1 ohm wire wound resistors (5watt each) in series and use a clip to tap off the voltage you need.

Back to back LM317's! One does one half of the wave the other does the reverse half.
Dont forget the blocking diodes and reverse diodes!