Shell of medium size for this genus, 3.8-4.5 mm in length and 2.3-2.9 mm in width, dextral, elongate-ovate, slightly thin, pale, translucent, about 6.5 whorls. Protoconch round, smooth, glossy and oblique compared to shell axis, apical whorls sharp. The body whorl increases rapidly, covering approximately 80 % of the total shell height. Suture deeply incised with a granulous spiral rib. Spiral ribs appear on last three or four whorls and become stronger as the whorls increase. Last 3-4 spiral ribs on the body whorl are conspicuously strenghtened and the one near the umbilicus upraises sharply and partly covers the umbilicus. 10-12 prominent spiral ribs and about 35 axial ribs on the body whorl. Axial ribs thinner than prominent spiral ribs. Between one to three pairs of adjacent prominent spiral ribs on the top and middle of the body whorl, a weak spiral rib exists. Spiral and axial ribs intersect to form a reticulate pattern. Umbilicus deep, elongate and wide. Columella slightly curved. A protuberance extends outwards the columella on the lower border of the umbilicus and the size and shape of this protuberance vary with each individual. Aperture semilunar, slightly oblique. Peristome simple to crenulated. Spiral ribs of some individuals protrude distinctly, which forms obvious serrations on the margin of the outer lip.

This species is closest to Macromphalus backeljaui Poppe, Tagaro & Stahlschmidt, 2015 in shell morphology by sharing a similar outline with similar length-width proportion of each whorl, semilunar apertural shape and a sharp upraising on the border of the umbilical area, while Macromphalus jinyuae sp. nov. is smaller in size and has a narrower umbilicus and strengthened spiral ribs on the bottom of the body whorl. Moreover, these two species have different sculpture patterns: 22-24 spiral ribs and around 35 axial ribs can be observed on the body whorl (dorsal view) of M. backeljaui, while M. jinyuae sp. nov. shows only a half the amount of axial ribs and prominent spiral ribs mingled with 1-3 weak spiral ribs (same view). Both spiral and axial ribs of M. jinyuae sp. nov. are stronger than those of M. backeljaui. As a consequence, the reticulate sculpture formed by the crisss-crossed ribs is sparser and more outstanding in M. jinyuae sp. nov..

Compared with Macromphalus styliferinus (Nevill, 1884): this species is larger in size and has a less developed umbilicus and a less sharp spire with more inflated last second and third whorls.

Macromphalus subreticulatus (G. Nevill, 1885) has a wider umbilicus, stronger spiral ribs and a less increased body whorl.

Macromphalus reticulatus S. V. Wood, 1842 has a deeper suture, a less increased body whorl and weaker sculpture patterns.

Macromphalus yamamotoi (Habe, 1978) has denser and finer ribs, a curved columella and a larger body whorl.

Macromphalus walkeri Poppe, Tagaro & Stahlschmidt, 2015 has a thin shell with almost invisible spiral lines, a deeper suture and the outer lip strongly expanded.

Type material: Holotype: Height: 4.5 mm, width: 2.9 mm. Coll. MBM, Qingdao, China. Collection number: MBM287544. China, Fujian Province, Xiamen City
Type locality: China, Fujian Province, Xiamen City, Siming District, Xiajinwan
Distribution and habitat: Known from Xiamen, China and only recorded in narrow areas of Xiajinwan and Guanyinshan in the east of Xiamen Island.
All specimens were collected from shell grit with sand sediment along the seashore, while the habitat of this species remains unknown.