The invention discloses a glass cleaning agent. The glass cleaning agent comprises components in percentage by mass as follows: 31.9%-65.2% of alcohol, 0.2%-0.5% of a surfactant, 0.1% of essence, 0.5% of an antifoaming agent, 1% of a dodecenyl imidazoline antirust agent and 33%-66% of water, wherein the surfactant comprises an anionic surfactant and a nonionic surfactant in the mass ratio being (1:1)-(1:3); the preparation method of the dodecenyl imidazoline antirust agent is as follows: oleic acid and diethylenetriamine react firstly and then perform condensation, 2- heptadecenyl-N-aminoethyl imidazoline is generated and has a neutralizing reaction with dodecenylsuccinic acid, and the dodecenyl imidazoline antirust agent is prepared. The decontamination ability of the glass cleaning agent is improved and cannot be reduced basically at the low temperature; the glass cleaning agent is not affected by seasons and regions and is more widely applied while compared with the prior art.