QTZ40 tower crane, as the latest model in domestic market at end of 20th century, is a hydraulic auto-lift tower machine characteristic of upper-circumgyrating, horizontal arm and variable range with small cabin. The lifting moment is 400KN.m, the independent installation height is 29m, and with attachments the lifting height can reach 120m. The maximum load is 4t. There are two specifications of work range: 42m, 46.8m,50m.