<p>The CT110 coiled tubing, known for its high strength, excellent compressive properties and long fatigue life, holds significant value in oil and gas field development. However, its damage evolution behavior under complex stress conditions remains poorly understood. In this paper, a fatigue damage model of CT110 coiled tubing is established based on Lemaitre damage theory; the damage variable D is expressed by the elastic modulus change method which is convenient for nondestructive testing in engineering, so as to predict the life of coiled tubing. This study establishes a Lemaitre fatigue damage model for CT110 coiled tubing based on damage theory. Through uniaxial tensile and cyclic loading tests, the key damage parameters of conventional and welded specimens, such as strain damage threshold, strain critical damage value and critical damage variable, were obtained. The accuracy of the CT110 coiled tubing fatigue damage model was validated by PLD-5 fatigue test and finite element simulation. The damage evolution process of CT110 coiled tubing under different cyclic loading conditions was analyzed. The paper also obtained the fitting relationship between the damage variables of CT110 continuous tubing and the number of cycles under the relatively wide used internal pressure of 35MPa in engineering, which provided a theoretical basis for predicting the service life of CT110 coiled tubing in practical engineering applications.</p>