The force of the taper pipe in the fully restrained section in a directly buried heat-supply pipeline and pipe section of both flanks of the taper pipe were analyzed with theoretical analysis and engineering practice.The maximum allowable cycle temperature differences were given for the primary and the secondary-stage taper pipes under different pressures.The results show that the weak link of the taper pipe is located in the junction of the small head and the small pipe.The taper pipe doesn't need any protection under maximum allowable cycle temperature differences.If the taper pipe is located in the partly restrained section

it also possibly doesn't need to be protected

that is related to its position.Except these

protective measures are necessary.The study has certain reference value for engineering practice.