The invention relates to a preparation method of internal pressure type hollow fiber composite membrane module, the preparation method comprises the following technical processes: 1. conventional equipment is adopted to weave an internal pressure type hollow fiber ultra-filtration membrane; 2. the membrane module is manufactured using the ultra-filtration membrane in the step 1 and leakage detection is performed; 3. the qualified membrane module is placed into coating solution for 30 seconds to 10 minutes for immersion coating and the temperature for immersion coating is 15 to 45 DEG C; 4. the inner wall of the membrane of the coated membrane module is blown and swept with dry and clean compressed air or N2, the water content of the membrane surface is controlled from 5 to 30 percent; 5. the cleaned membrane module is dipped in cross-linking fluid which is used for realizing interface reaction to produce the composite membrane or the cross-linking fluid is infused into the inner cavity of the membrane from the upper end of the membrane module to produce the composite membrane; 6. the membrane module which has completed cross-linking reaction is immediately immersed into water bathand is sealed up for future usage, thus, the internal pressure type hollow fiber composite membrane module is obtained.