Abstract: The application of cast titanium alloys in steering knuckles represents a new direction, and the fracture analysis of these materials has also attracted much attention. The cast titanium alloy steering knuckle of a certain car fractured during vehicle testing. The fracture surface initiated at the chamfer surface and propagated toward the interior.This paper conducted a comprehensive analysis of the failed steering knuckle fracture surface by methods such as macroscopic analysis, chemical analysis, mechanical property analysis, metallographic analysis, and scanning electron microscope (SEM). The results showed that the fracture mode of the titanium alloy steering knuckle belonged to fatigue fracture. The chemical composition and mechanical properties of the steering knuckle both met the requirements for ZTC4 titanium alloy as stipulated in the relevant standards. The metallographic structure was normal. However, the processing quality of the outer surface at the fracture initiation position was poor, and there were rough machining tool marks. This led to stress concentration, and the crack initiated at the machining tool marks and rapidly propagated, causing the steering knuckle to fracture.