The invention discloses an MCM-22 molecular sieve in the form of cavity aggregation and a preparation method thereof. The molecular sieve is 5-30 [mu]m and preferably is 10-20 [mu]m in size. A wall of each cavity is formed of MCM-22 micro crystalline grains being 20-200 nm, preferably 50-100 nm. The wall of each cavity is 0.2-3.0 [mu]m in thickness, preferably 0.5-2.0 [mu]m. The preparation method includes the following steps: 1) uniformly mixing an aluminum source, a silicon source, alkali, water, polyethylene glycol, sodium lignosulphonate and a template agent; 2) continuously mixing the mixture under both ultrasonic dispersion and mechanical stirring; 3) crystallizing the material obtained in the step 2), and washing, drying and roasting a product to prepare the MCM-22 molecular sieve in the form of cavity aggregation. The MCM-22 molecular sieve is uniform in particle and is strong in controllability. The structure is beneficial to mass transmission of materials. The template agent is low in cost and easy to obtain and is easy to burn away, so that the MCM-22 molecular sieve is less in generated emission and is low in environment pollution, and has unique application prospect in the field of alkylation reaction on olefins.