While similar to the related Huaxiagnathus, Sinocalliopteryx were larger. The type specimen, at 2.37 meters (7.78 ft) in length, in 2007 was the largest known compsognathid exemplar. In 2012 an even larger specimen was reported.
Sinocalliopteryx was a bipedal predator. The preserved length of the holotype specimen is 237 centimetres. Its weight was estimated by Gregory S. Paul in 2010 at twenty kilogrammes. Sinocalliopteryx is distinguished from Huaxiagnathus, as well as other compsognathids, by its relatively long hands in relation to its arms. The arms and hindlimbs were also longer overall than in other compsognathids, a feature possibly related to its size.
Sinocalliopteryx had an elongated head with a pointed snout, showing a convex upper profile. There were four teeth in the premaxilla which were small but exceptionally had denticles on their front edges. Only six, larger, teeth were present in the maxilla of the holotype specimen but the number of its tooth positions could not be adequately determined. Specimen CAGS-IG-T1 preserves ten maxillary tooth sockets with room for one or two more in damaged areas. The jugal was a strongly built element with a high-rising front branch that formed part of the lower front edge of the eye socket. The lower jaw lacked an opening in its outer side.
The vertebral column consisted of eleven cervical, twelve dorsal, five sacral and at least forty-nine caudal vertebrae. The point of the tail is missing. In the tail, the spines and chevrons strongly inclined to the back. The gastralia had very short lateral segments.
The arm had a short humerus and also the lower arm was short and elegant with an ulna showing only a weakly developed olecranon process on its back upper end. The hand was very elongated though, as long as the ulna and upper arm combined. The second metacarpal was expanded at the top at the side of the first metacarpal, making the entire metacarpus more compact. The second claw was elongated, as long as the thumb claw. The third metacarpal was rather short and carried a thin, third, finger.