The output is distorted before it reaches the saturation voltage.

In the saturation concept of OPA, if the output does not reach +-VCC, the Vout of OPA will not be distorted.
But I don’t understand why it is distorted when I input a +-1V sin wave at the Vin ,(I zoomed in 17 times, so Vin can normally input +-1.4V sin wave).
Below is my circuit and waveform.
 

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But I don’t understand why it is distorted when I input a +-1V sin wave at the Vin ,(I zoomed in 17 times, so Vin can normally input +-1.4V sin wave).
Your upper TIP41 has insufficient base current available. As the output swings higher toward Vcc the voltage across the 500 ohm reduces even more leaving no base current being available. At 15 volts peak output voltage you have leaves just 9 volts across the 500 ohm which is just 18 milliamps. In reality you need a few hundred milliamps base drive current to be available.