起重机主要包括起升机构、运行机构、变幅机构、回转机构和金属结构等。起升机构是起重机的基本工作机构，大多是由吊挂系统和绞车组成，也有通过液压系统升降重物的。运行机构用以纵向水平运移重物或调整起重机的工作位置，一般是由电动机、减速器、制动器和车轮组成。变幅机构只配备在臂架型起重机上，臂架仰起时幅度减小，俯下时幅度增大，分平衡变幅和非平衡变幅两种。回转机构用以使臂架回转，是由驱动装置和回转支承装置组成。金属结构是起重机的骨架，主要承载件如桥架、臂架和门架可为箱形结构或桁架结构，也可为腹板结构，有的可用型钢作为支承梁。
Crane mainly includes lifting mechanism, running mechanism, luffing mechanism, slewing mechanism and metal structure. The hoisting mechanism is the basic working mechanism of crane, which is mostly composed of hanging system and winch, and lifting heavy objects through hydraulic system. The running mechanism is used to move heavy objects vertically and horizontally or to adjust the working position of the crane. It is generally composed of motor, reducer, brake and wheel. The luffing mechanism is only equipped on the jib crane, and the amplitude decreases when the boom is lifted up and increased when it is lowered. It is divided into balanced luffing and unbalanced luffing. The slewing mechanism, which is composed of driving device and slewing bearing device, is used to rotate the boom. Metal structure is the skeleton of crane. The main bearing parts such as bridge, jib and portal frame can be box structure or truss structure, or web structure. Some of them can be used as support beam.