Abstract: Objective Natural hazards and disasters in China have increased in magnitude and frequency in recentyears as consequences of the fast urbanization promotion and global climate change,which has greatlythreatened to the sustainable development of social economy.The widespread devastation,economicdamages and loss of human lives,caused by numerous forms of natural emergency situations,are be-coming more serious.The emergency surveying and mapping service system(ESMSS),which is ableto make practical contributions to planning and operation of civil protection and disaster reduction,isurgently needed.The paper probes into some key techniques involved in the construction of theESMSS at first.Taking applications in“4·20”Lushan earthquake as an example,the article deeplyanalyses the problems in data acquisition,transmission,processing,distribution,sharing of the cur-rent ESMSSs and their working mechanism.Then,the construction method of the proposed task-driven ESMSS is presented in details.Finally,the key techniques including focused service mechanismare expounded.