Based on the electromagnetic field theory,deduduced electric attractive force calculation formula of electromagnet used to ADS valve of shock absorbers in this paper. According to the external form of electromagnet, designed an experimental system measuring the mechanical properties of sucker electromagnet. By measuring the mechanical properties of sucker electromagnet, combining experimental data and analytical results indicate that the formula derived with very high accuracy. For the electromagnet used to ADS valve of shock absorbers research and design the formula provides theoretical value.