Experimental research was performed to investigate the start-up characteristics and heat transfer performance of double-row pulsating heat pipe (PHP) with connecting pipe structures under horizontal and vertical placements. In the condenser section, there were five turns in each row of the double-row symmetrical structure, and in the evaporation section, there was a common connecting pipe. Deionized water was the working fluid, and a 50% filling ratio was used. The experimental approach involved investigating the connected and disconnected cases independently to determine the impact of the connecting pipes on the efficiency of the heat transfer and start-up processes. Infrared thermography was used to analyze the temperature distribution on the pipe wall and determine the working fluid flow status. According to the experimental findings, the start-up time and thermal resistance were 550 s and 0.48 K/W, respectively, when mounted vertically and connected. The start-up time rose 2240 s and heat resistance rose by 4% when the connecting pipe was disconnected. The connecting pipe had the opposite impact when the PHP was installed horizontally than when installed vertically. When the connecting pipe was disconnected, the start-up ability and heat transfer performance were improved.