The invention discloses a preparation method of low-cost ZSM-5 type zeolite molecular sieve, and application of the low-cost ZSM-5 type zeolite molecular sieve, belonging to the field of a molecular sieve preparation technology. The method comprises the steps of a. drying pulverized fuel ash raw powder to constant weight, mixing HCl solution with the dried pulverized fuel ash, stirring, centrifuging, washing and drying for later use; b. grinding the pulverized fuel ash treated by the step a, mixing the ground pulverized fuel ash with NaOH for melting, cooling, grinding and screening by a molecular sieve; feeding the ground melt into deionized water, mixing, stirring under the condition of water bath, and carrying out centrifugal separation to obtain liquid supernatant; c. taking the liquid supernatant obtained in the step b, taking tetrapropylammonium hydroxide as a template agent and NH4F as a mineralizer, mixing and carrying out crystallization reaction; after that, taking out the product, quenching to the room temperature, washing, drying and roasting to obtain the zeolite molecular sieve. According to the method, the pulverized fuel ash discharged by a thermal power plant is fully utilized as a silicon-alumininm source and is used for replacing pure chemical reagents Si and Al for synthesizing the molecular sieve, so that the synthesis cost of the molecular sieve is lowered, and the utilization value is high.