The invention provides a preheating method applied before oil production adopting double horizontal wells and an oil production method adopting the double horizontal wells. The preheating method applied before oil production adopting the double horizontal wells comprises the following steps: steam is injected into a first steam injection pipe arranged in a steam injection well and a second steam injection pipe arranged in a production well, and a downhole liquid is drained through a first drainage pipe arranged in the steam injection well and a second drainage pipe arranged in the production well, so that the degree of communication between the steam injection well and the production well reaches a preset value. According to the preheating method applied before oil production adopting the double horizontal wells, the steam is injected into an oil reservoir through the first steam injection pipe arranged in the steam injection well and the second steam injection pipe arranged in the production well simultaneously to heat the oil reservoir, whether the double horizontal wells are well prepared for production is determined by detecting the degree of communication between the steam injection well and the production well, the oil reservoir is preheated sufficiently by the double horizontal wells, so that the oil reservoir is endowed with good production conditions, and higher crude oil yield can be realized when oil production is performed at the moment.