Four different kinds of ferrofluid, which were applied into the experiment of differential pressure sensor, were prepared by chemical co-precipitation method. The density, viscosity and magnetization intensity of ferrofluid were analyzed and the influence of the parameters on the differential pressure sensor were measured in experiments which were designed to verify the theory analysis. The relation between the sensitivity of differential pressure sensor and the density and magnetization of ferrofluid were linear in a certain range. but with increasing of density and magnetization, the curve gradually leveled off when the ferrofluid was saturated. The Sensor response time was lengthened with the increasing of viscosity of the ferrofluid.