NOVELTY - Preparing biological diesel by coal-based methanol and palm oil supercritical method comprises continuously feeding coal-based methanol and palm oil in a ratio of 30:1-40:1 to a preheater, premixing and pre-heating at 300-350 degrees C, then conveying to a tube-type reactor, under the condition of without adding catalyst, subjecting methanol and oil to transesterification reaction under supercritical state to obtain bio-diesel and glycerol, where the reaction temperature in the tube-type reactor is 300-350 degrees C, the reaction pressure is 15-20 Mpa, and reaction time is 5-15 minutes.    USE - The method is useful for preparing biological diesel by coal-based methanol and palm oil supercritical method (claimed).    ADVANTAGE - The method: utilizes easily available raw materials; has low cost; does not require catalyst; produces good quality biodiesel; avoids the corrosion and difficult to separate the product from the catalyst in the traditional catalytic supercritical device of acid-base catalyst; is environmentally friendly; and has methyl ester conversion effect.    DETAILED DESCRIPTION - Preparing biological diesel by coal-based methanol and palm oil supercritical method comprises continuously feeding coal-based methanol and palm oil in a ratio of 30:1-40:1 to a preheater, premixing and pre-heating at 300-350 degrees C, then conveying to a tube-type reactor, under the condition of without adding catalyst, subjecting methanol and oil to transesterification reaction under supercritical state to obtain bio-diesel and glycerol, where the reaction temperature in the tube-type reactor is 300-350 degrees C, the reaction pressure is 15-20 Mpa, and reaction time is 5-15 minutes, purifying the reaction product under reduced pressure to obtain crude biological diesel and crude methanol, distilling the crude bio-diesel to obtain high purity biological diesel oil and residual oil, distilling the crude methanol gas to obtain high purity methanol, then returning to palm oil, and recycling. An INDEPENDENT CLAIM is also included for device for preparing biological diesel by coal-based methanol and palm oil supercritical method, comprising methanol storage tank (1) through a first plunger pump (2) connected with a pre-heater (5). An oil storage tank (3) through a second plunger pump (4) is connected with the preheater. The pre-heater is connected with a tube type reactor. The tube-type reactor is connected with a gas-liquid separator, and provided with a decompression valve. The gas-liquid separator is connected to a pressure reducing rectifying tower through a pump. The gas-liquid separator is connected to methanol rectifying tower. The methanol rectifying tower is connected to the methanol storage tank. The methanol rectifying tower is connected with the gas-liquid separator. The pressure reducing rectifying tower is connected with a vacuum pump.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device for preparing biological diesel by coal-based methanol and palm oil supercritical method.    Methanol storage tank (1)    First plunger pump (2)    Oil storage tank (3)    Second plunger pump (4)    Pre-heater (5)