[Objectives]  To determine the morphological characters of Anopheles sinensis Wiedemann, an important vector of malaria in China, and thereby provide a reference for the identification and classification of the Hycanus group. [Methods]  Samples were fixed with 1% osmium acid and 6% glutaraldehyde, and specimens of different developmental stages prepared for electron microscopy by combining dehydration at different ethanol concentrations with tert-butanol vacuum freeze-drying. Morphological characters were observed and recorded using a Hitachi SU3500 electron microscope at 5 kV voltage in the SE (secondary electron) mode. [Results]  There was little sexual dimorphism in beak or antennae length. Adult males have horsetail tentacles with enlarged, curved ends and circular-cake pedicels and the tail organs at the end of their abdomen have a pair of pincer-like arms. Adult females have slender beaks and serrated upper and lower jaws, which are used for piercing human skin and sucking blood. Their pedicels are full and spherical and the tail organs at the end of the abdomen have a pair of inwardly curved tail whiskers that are obviously shorter than the male’s pincer-like arms. Electron microscopy revealed that the respiratory tubes of the tadpole-like pupa are on the head and have an acute triangular opening with a smooth circle of blunt teeth at the edge. The fan-shaped caudal fin is two-petaled. The external genitalia of male pupae are obviously longer than those of female pupae. 4th instar larvae have a linked thorax and abdomen, spiny receptors on the antennae, and a valve on dorsal end of the 8th abdomen segment. The eggs are boat shaped and have a larger surface area than the eggs of other mosquito species. Eggs have evenly distributed, small, granular protrusions on their surface, most of which are arranged in a hexagonal pattern. Eggs also have flat, fine pores at their dorsal ends. [Conclusion]  The respiratory tubes of pupae and the external morphology of eggs are important characteristics for identifying A. sinensis. These results not only provide valuable information for identifying A. sinensis but also aids mosquito-borne disease control.