In this paper, by studying the different kinds of jetting system in patternless casting manufacturing (PCM) technique, the different types of jetting mode are tested which affect whether PCM process can be done successful. The two different kinds of jetting device and their control circuits are designed based on which the relationship between the jetting system and amount of the catalyst flow is analyzed. The experiments show that the amount of the catalyst by using discrete jetting mode in the discrete jetting device is much lower than that by using continuous jetting mode in the discrete jetting device and in the continuous device when the pressured is fixed. At the same time, in the discrete jetting mode the amount of the catalyst flow can also be changed by adjusting the pulse frequency and its duty cycle, this can ensure the strength of the sand mould. The flow of catalyst in this discrete jetting device can match the scanning speed of the jetting device in real time which will improve the resolution and building precision of casting mould. When the amount of the catalyst jetting is too large, PCM process will fail. In this paper, by studying the different kinds of jetting system in patternless casting manufacturing (PCM) technique, the different types of jetting mode are testing which affect that PCM process can be done successful. The two different kinds of jetting device and their control circuits are designed based on which the relationship between the jetting system and amount of the catalyst flow is is analyzed. The experiments show that the amount of the catalyst by using discrete jetting mode in the discrete jetting device is much less than that by using continuous jetting mode in the discrete jetting device and in the continuous device when the pressured is fixed. the same time, in the discrete jetting mode the amount of the catalyst flow can also be changed by adjusting the pulse frequency and its duty cycle, which can ensure the strength of the sand mold. The flow of catalyst in this discrete jetting device can match the scanning speed of the jetting device in real time which will im prove the resolution and building precision of casting mold. When the amount of the catalyst jetting is too large, PCM process will fail.