Marine insurance contracts, which intended to provide indemnity againstmarine risks upon the payment of price, known as a premium, originatedin Northern Italy in the late 12th and early 13th centuries. The law andpractice were later introduced into England through the Continent. It is,therefore, quite exact that English and European marine insurance lawhave common roots. Nevertheless, significant divergences between Englishand European insurance systems occurred since the late 17th century,mainly due to different approaches adopted by English courts.The rule of warranty in English marine insurance was developed andclarified in the second part of the 18th century by Lord Mansfield, wholaid the foundations of the modern English law of marine insurance, anddeveloped different approaches, especially in the field of warranty inmarine insurance law. Since the age of Lord Mansfield, English marineinsurance law has a unique rule on warranty. This article is, therefore,designed to analyse the overall rule of the rule of warranty in Englishmarine insurance law. The result of analysis are as following.First, warranties are incorporated to serve a very significant function inthe law of insurance, that is, confining or determining the scope of thecover agreed by the insurer. From the insurer's point of view, such thefunction of warranties is crucial, because his liability, agreed on thecontract of insurance, largely depend on in, and the warranties,incorporated in the contract play an essential role in assessing the risk. Ifthe warranty is breached, the risk initially agreed is alteredand that servesthe reason why the insurer is allowed to discharge automatically furtherliability from the date of breach.Secondly, the term 'warranty' is used to describe a term of the contractin general and insurance contract law, but the breach of which affordsdifferent remedies between general contract law and insurance contractlaw.Thirdly, a express warranty may be in any form of words from whichthe intention to warrant is to be inferred. An express warranty must beincluded in, or written upon, the policy, or must be contained in somedocument incorporated by reference into the policy. It does not matterhow this is done.Fourthly, a warranty is a condition precedent to the insurer's liability onthe contract, and, therefore, once broken, the insurer automatically ceasesto be liable. If the breach pre-dates the attachment of risk, the insurerwill never put on risk, whereas if the breach occurs after inception ofrisk, the insurer remains liable for any losses within the scope of thepolicy, but has no liability for any subsequent losses.Finally, the requirements on the warranty must be determined inaccording to the rule of strict construction. As results, it is irrelevant: thereason that a certain warranty is introduced into the contract, whether thewarranty is material to the insurer's decision to accept the contract,whether or not the warranty is irrelevant to the risk or a loss, the extentof compliance, that is, whether the requirements on the warranty iscomplied exactly or substantially, the unreasonableness or hardship of therule of strict construction, and whether a breach of warranty has beenremedied, and the warranty complied with, before loss.