Xu Wei once said that when painting his subjects, he never sought verisimilitude but aimed to capture their spirit. To achieve that goal, he unleashed his brush with passionate abandon in his ink paintings, galloping vertically and horizontally across his canvas and dripping ink on the paper without any restrictions. As both a calligrapher and a painter, Xu integrated his calligraphy skills and techniques into his ink paintings to infuse them with greater energy and presence.

In the view of Beijing Normal University Professor Kang Zhen, Xu's unrestrained brushwork relates to his turbulent life. Born to a waning powerful family, Xu attempted to pass the civil service examinations eight times without any luck. So in his later years, he was able to use all of his past grief and express this whirlwind of torment and emotion with his brushwork, using lines of varying size, hurried texture strokes, and wet and diluted ink.

The acclaimed shrimp painter Qi Baishi once said, "How I wish I had been born 300 years earlier so I could grind ink and prepare paper for Green Vine (one of Xu Wei's pen names)." By using swaying and indulgent brush and ink techniques, Xu not only depicted his subjects clearly and simply but also expressed his own strong emotions in his art. Such pioneering efforts were highly appreciated by future generations, ultimately pushing Chinese freehand paintings of flowers and birds to a whole new level.