Annual climbing herb, smooth and glabrous, covered with hoarfrost. The root system is developed and there are many round nodules. The stem is cylindrical, hollow and brittle, with branches. Dwarf varieties are 30 ~ 60 cm high, and creeping varieties are more than 2 meters high. Double pinnate compound leaves with 2 ~ 6 leaflets, and tendrils have pinnate branches at the top of leaf axis; Stipules are leaflike, usually larger than lobules, with sparse teeth at the lower edge; Leaflets are ovate or oval, 2 ~ 5 cm long and 1 ~ 2.5 cm wide, with blunt or sharp apex, wide wedge-shaped or round base, entire, and sometimes sparsely toothed. Flowers are solitary or axillary, and 2 ~ 3 flowers are born on the peduncle; Flowers white or purple; Calyx campanulate; The corolla butterfly pod is cylindrical, slightly flat, 5 ~10cm long and1~1.5cm wide, and contains 3 ~ 10 seeds. After drying, the seeds are spherical, oval or oblate, blue-green, yellow-white, green and brown, and the seed coat is smooth with wrinkles or folds. Chromosome 2n= 14.