LM2576 on/off circuit
i want it turn on for example when input voltage is above 10 volt and
turn off when input voltage is below 10 volt .

I see what you mean - the control is inverted and doesn't easily lend itself to adding a simple potential divider however, it might be a mistake not to consider that some level of hysteresis is required. For instance, when the voltage is above 10.1 volts it turns on and when the voltage drops below 9.9 volts it turns off. This prevents the device turning on and off rapidly around the single threshold of 10.0 volts.
So, to achieve what you want use an inverting comparator circuit with variable thresholds set by hysteresis. This is the standard circuit without hysteresis: -

Picture taken from here.
And here I've added in a resistor in red that brings about a little hysteresis: -

In this circuit, Vcc would have to remain constant in order to achieve what you want. There are some low voltage comparators that can be directly run from the incoming power rail by using a zener diode and series resistor and this may be more attractive to you. I designed one recently (just the comparator and reference) here. You should be able to invert that design and figure how to apply a zener regulator to it.