This paper introduces the forms of quenching cracks on thirteen truck parts including crankshaft and half axle, It discusses the causes resulting in the cracks such as improper shape, dimension, surface finish, drastic or non-unlfors quenching and the chemical coapositions of the satsrial. It also explores the ways of prevention.Induction heat treatment is an advanced technology of heat treatment which provides high effective production, no environmental pollution, facilities for automatization and energy saving. This technology has been developing rapidly since it appeared for the first time. Some articles in troduced that if the installation capacity for induction heating equipment was 100 in the United States in 1965 and 400 in 1985, it increased by 3 times. Automobile industry is the biggest user of induction heat treatment technology. Other articles introduced that the weight of induction hardened parts on two types of mass-produced trucks in USSR respectively attained to 235.5 and 285.5 kg, as well as possessed of 58.2 and 68.1% of the total weight of the heat-treated parts. The varieties of induction hardened parts for a mass-produced Chinese truck are more than 60, their weight is 260 kg or so, and occupies 46.4% of the total weight of heat-treated parts.All kinds of quality problems may occur during induction hardening of those parts. The most conspicuous problem is quenching cracks. They vary in form, the reasons are complicate and the hars are serious, anyhow these problems can be understood and prevented as well as other quality problems. Various factors causing quenching cracks and their preventive measures are discussed below.