By using a new synthetical testing instrument SMT-1 the mechanical properties and electrical resistance of TiNi shape memory alloy on loading, in recovery process and under a restraint (stress or strain) condition have been studied and the mechanism has been discussed. The results showed that the electrical resistance-strain curve on loading reveals the stress induced martensitic phase transformation clearer than the stress-strain curve; the recovery temperature increases with tensile strain; the recovery stress-temperature curve under a restraint strain depends on the strain; the strain produced by martensitic phase transformation under a constant stress is much larger than that without a constraint stress. The results also showed that the synthetical measurement of stress, strain, electrical resistance and temperature is a very effective method to study the properties and structure of shape memory alloys.