Mainly depends on the pen, pen and ink, emotion, style, artistic conception, genre style, composition, signature era characteristics and personal style. Calligraphy and painting are works, which will inevitably leave the characteristics of the times. The characteristics of calligraphy and painting in different times are different. I'm afraid it's hard to believe the landscape paintings before the Tang Dynasty, and no one believes in using regular script as the calligraphy of the Western Han Dynasty. As long as you have a general understanding of the age, style and style of calligraphy and painting, you can identify obvious counterfeiting. For famous works, we should not only understand the life, artistic style and creative subject range of famous works, but also understand their pen and ink techniques. The artistic expression of famous artists is formed through long-term practice, and it is inevitable that ordinary people will fail to imitate. If they grasp the characteristics of someone's brushwork and study it deeply, it will be easy to identify fakes.