I connect LED 12V 1W to arduino but LED few bright.

I connect LED 12V 1W series 4 LED to pin C of transistor BC547 and connect pin B of BC547 to arduino. but LED series little bright not very bright like when I connect direct to power supply. when have output 5V from arduino LED 12V 1W should very bright like connect direct to power supply. How to fix it ?

Wire it up correctly.
Where is the emitter?
Where is your base resistor?
Are your grounds connected up?

are you trying to run a 12v led series which is designed to be operated on a 12v power supply.
USB provides only 5v so it would only glow dimly as the voltage is below that required to properly drive the LED series.
to run the LED brightly you would need an external power supply through the dc in socket at 12v, or use a 5v relay to switch a seperate power supply and the LED series.

If you do power the arduino from 12 then depending on the LED series, you might be able to dim them with PWM commands (pulse width modulation) which the arduino supports

I connect like this . LED little bright but when I connect direct to power suppply it very bright. I think BC547 may limit current. How to make LED very bright when connect to arduino.

If you put them in series each one will only receive 3V.

4x 12v 1 watt = 4 watt.
watts = volts * amps
therefore watts divided by volts = amps
therefore 4 watts divided by 12 = 0.333... amps. or 333.3 milliamps of current needed to drive them.

You show them in series. each 12v led will have a voltage drop across it therefore they are not actually running at 12v. they may actually be getting less voltage than they like thus running dim.

have you tried to run two parallel LED strings each of two led's so each gets a higher voltage.
the current drain may be higher on the battery but the led's should glow brighter.

I played around with led's when i was building a raygun as part of a costume which had 16 2.2-2.4v leds (each colour 2x2 leds)

10kOhm from arduino 5V to base provides about 0.44mA
h_fe * 0.4mA = "not very bright"; probably about 12mA and not the 333mA which you want.

Connect a second transistor from your arduino with 10k to its gate to drive a measured 10mA through a resistor above it from 12V.
Now move the e of that second transistor from ground to go through 100Ohms or so to the gate of your first transistor. Your first transistor can now conduct up to h_fe * 10mA, which might be about right for "very bright".

You can change the resistor above this extra transistor to change the brightness.

You can not control a power led like this. While at the moment you do not have about current due to the high value of base resistor and low voltage across each LED when you rectify this you will have nothing to limit the current and things will melt.
You need a constant current drive and a higher voltage.

I connect two parallel LED it not very bright. So, I connect one parallel LED I think all LED not bright egual some LED very bright and some LED not very bright. I have to use this circuit with battery. How to create low power circuit for drive LED 12V1W with arduio.

How to create low power circuit for drive LED 12V1W with arduio.

I have no idea what you mean because a load of 1W is not low power.

How many LEDs do you want to light up? What are these LEDs, specifically do you know their forward voltage drop?

Do not connect raw LEDs in parallel they will not share current.