Disclosed is a long-acting slow-release pharmaceutical preparation. The pharmaceutical preparation contains 25%-60% of a water-insoluble or sparingly-soluble drug and 40%-75% of a high-molecular polymer. After the pharmaceutical preparation is subjected to one time of intramuscular injection administration, the ratio of a maximum plasma concentration to a minimum plasma concentration in a main release period is less than 5; the slope of a linear trend line of a cumulative release curve is less than 8 under an in-vitro simulated release condition; the daily release amount is less than 8.5%; and the simulated release condition is a buffer solution with the temperature of 37?.5癈 and the pH of 6.5-8.4. The prepared long-acting slow-release pharmaceutical preparation in the present invention has the beneficial effects that an obvious release delay period or a burst release phenomenon are avoided after administration, a steady state plasma concentration can be quickly achieved, the plasma concentration with a relatively small fluctuation range can be maintained in several weeks or longer after single administration, and the pharmaceutical preparation can take effect quickly and has good compliance with a patient.