The first reactor of HPR1000 is 0.3 g gravity acceleration and the original EM9 installation document is no longer applicable. The structural form and support setting of seismic instrument pipelines need to be studied and principles provided. This article studies seismic structural form and support setting method of instrument pipelines for the above changes. It establishes the principles, grading, load rules and criterion levels for instrument pipeline layout, analyzes and studies seismic instrument pipeline samples of the whole Hualong First Reactor plant, optimizes support setting method, proposes seismic pipeline structure and new design principles. The envelope design verification is performed by selecting typical instrument pipelines of the plant. The research results are applied to Fuqing 5&6 projects and subsequent engineering, which can meet seismic requirements of HPR1000 with gravity acceleration of 0.3 g and have high application value, contributing EM9 wisdom to mass construction of HPR1000.