According to the characteristics of carbonate reservoir of Iraqi Missan oilfields，an acidic completion fluid for protection of carbonate reservoir was prepared using a weak corrosion solid acid HTG as main agent，in which NaCl combined with HCOONa brine was selected to adjust the density of the completion fluid and a corrosion inhibitor JCI was added to control the corrosion of pipe string. The formula of the completion fluid was as follows：25% NaCl + 10% HCOONa + 3% HTG solid acid + 3% JCI corrosion inhibitor. The flushing ability of completion fluid to mud cake formed by drill-in fluid，gel breaking ability，compatibility of completion fluid with the filtrate of drill-in fluid，and the reservoir protection effect of the completion fluid were investigated. The results showed that the corrosivity of the completion fulid was lower，and the mud cake formed by the drill-in fluids could be removed effectively by the completion fluid and the residues of the mud cake could be cleaned up without gel breaking procedure. The permeability recovery of the core，which was polluted by drill-in fluid and then treated by completion fluid，reached over 95%，which indicated that the ompletion fluid had good effects of reservoir protection.