His representative works include Autumn Chrysanthemum, Wutong Bird (collected by Beijing Painting Academy), Eight Horses, Peacock and so on. Ma Jin is a famous horse painter of the traditional Beijing School. When he entered the painting world from Lang Shining, it was the time when Kang Youwei advocated "combining Chinese and Western styles to form his own family" and "taking Lang Shining as the great ancestor". However, under the guidance of Jincheng and Chen Shiceng, Ma Jin not only extensively studied the traditions of ancient academy painting and literati painting, but also dabbled in calligraphy and seal cutting, and was able to correct copying by sketching. In 1930s and 1940s, when his meticulous realistic painting style was mature, he began to strengthen China flavor in his paintings. In 1950s and 1960s, he perfected his meticulous realistic style in horse, ox and flower-and-bird paintings, and introduced a small freehand brushwork style combining meticulous brushwork. Ma Jin's meticulous realistic works are full of sense of body and texture, informal, fine but not broken, clean and beautiful, appealing to both refined and popular tastes, which is far from Lang Shining's "cautious and subtle". His small freehand brushwork, simple and vivid, uses pen and ink, and works with pen. His works include the illustration "Bear Restaurant", a hunting child and a doctor aloff. In the early 1930s, a horse won the honorary certificate of Panama World's Fair.
His published works include: How to Draw a Horse, Ma Jin, A Collection of Paintings by Famous Modern and Contemporary Artists in China, Rong Baozhai Paintings141-Painting a Horse, Selected Paintings of Ma Jin, etc.