Belonging to the technical field of waste resource recycling, the invention provides a method for preparation of chitin, protein and organic acid calcium from shrimp shell by ionic liquid. The method includes the steps of: (1) using eutectic ionic liquid or a water solution thereof to remove calcium carbonate from shrimp shell powder so as to obtain calcium removed shrimp shell powder; (2) using phosphate ester ionic liquid to remove protein from the calcium removed shrimp shell powder to obtain an insoluble substance, i.e. a chitin product; (3) collecting the supernatant of step (1) and step (2) respectively, adding a stripping agent to conduct regeneration, thus obtaining the products organic acid calcium and protein respectively, at the same time collecting the supernatant, thsu obtaining the stripping agent-containing eutectic ionic liquid and phosphate ester ionic liquid. The method provided by the invention utilies waste shrimp shell to prepare high purity chitin, organic acid calcium and protein, and realizes comprehensive utilization of shrimp shell. At the same time, the ionic liquid used by the invention has no pollution, can be recycled and is low in cost.