The invention relates to a compound sweetener suitable for plant protein beverage and coffee and a preparation method of the compound sweetener. The compound sweetener comprises 13.33 to 25 percent of sucralose, 20 to 30 percent of isomaltitol, 20 to 30 percent of erythritol, 14.34 to 46.44 percent of glucose, 0.15 to 0.3 percent of carboxymethylcellulose, 0.03 to 0.06 percent of sclareolide and 0.05 to 0.3 percent of emulsifier. The preparation method comprises the following steps of: feeding the sucralose and sugar alcohol as well as 60 to 70 percent of the total glucose into a multi-dimensional mixing machine for preliminary mixing; mixing the residual glucose, the emulsifier and the like and water to form stable emulsion; enabling the mixture to enter a spraying fluidized bed from the bottom of the spraying fluidized bed under positive pressure and flow sy an accelerated speed from bottom to top, applying negative pressure to the upper part of the spraying fluidized bed, vibrating the mixture from top to bottom so that the mixture overturns up and down in the fluidized bed to form fine sugar alcohol particles; and continuously spraying and dispersing the emulsion to the small sugar alcohol particles in the fluidized bed to obtain the compound sweetener.