A method for preparing a NU-88 molecular sieve comprises the steps of dissolving inorganic base, an aluminum source and a template in water to perform uniform mixing; adding a silicon source into the mixture, and performing uniform mixing to obtain a colloid or solid-liquid mixture; wherein the molar ratio of SiO2:Al2O3:Me2O:R:H2O is (35-60):1:(9-15):(1-4):(700-1300), wherein R is the template, Me is Na or K, the template has 1,n-bis(N-methylpyrrolidine) alkylene positive ions as shown in formula (1), the number n of alkylene carbon is 2-6, ; transferring the obtained colloid or solid-liquid mixture into a crystallization kettle, and performing stirring and crystallization for 5-8 days under hydrothermal conditions of 120-200 DEG C, and washing and drying the obtained solid to obtain NU-88 molecular sieve raw powder. The method can improve single kettle yield and shorten crystallization time.