The invention relates to a metal cutting solution of green semi-synthesis double-base oil, which comprises the following components in percentage by weight: 0 to 30 percent of mineral oil, 0 to 30 percent of synthetic ester, 5 to 10 percent of anionic surfactant, 5 to 10 percent of non-ionic surfactant, 5 to 15 percent of anti-rust agent, 0 to 15 percent of extreme pressure agent, 1 to 3 percent of de-foaming agent and 0 to 2 percent of bactericide, and the balance being water. A preparation method for the metal cutting solution comprises the following steps: firstly, heating the mineral oil to about 50 DEG C, adding the synthetic ester into the mineral oil, and stirring the mixture evenly to form a double-base oil system; and then adding the anti-rust agent, the extreme pressure agent, the de-foaming agent and the bactericide into the water respectively, and using the anionic surfactant and the non-ionic surfactant to regulate the system to balance so as to form the metal cutting solution of the green semi-synthesis double-base oil. Because the synthetic ester is added in the preparation process to form the double-base oil system, the biodegradability, oxidative stability and flash point are improved; and the method meets the requirement of environmental protection, and is applicable to cutting, grinding and processing various mechanical parts.