Online car hailing is a specific application of internet technology in the field of travel. The change of the purpose of the insured vehicle by the policyholder results in a significant increase in the risk degree of the insured object. There are different views on whether the insurer should bear the insurance liability in judicial practice and theoretical research. The applicant changes the purpose of the insured vehicle without authorization, which not only violates the insurance contract, but also destroys the consideration balance of the insurance contract. The obligation of noticing a significant increase in the risk level belongs to the contractual obligation, and the applicant shall notify the insurer in accordance with the provisions of the insurance contract. The contract agreement about significantly increased risk level belongs to the exemption clause, and the insurer should clearly explain the obligation, otherwise it will not have legal effect. The insurance law should introduce the principle of proportionality to adjust when facing the significantly increased risk of online car hailing. The application of proportionality principle in the insurance liability of online car hailing is the proportion compensation, which not only effectively alleviates the rigidity of the significant increase of the risk level without notice of adverse consequences, but also further corrects the consideration balance of the insurance contract to ensure the interest balance of all parties to the insurance contract.