A chlorinefree composite as oilwell cement early strength agent named LL was developed. Combining organic acids A, alcohol amines B and nitrate compound C in a certain ratio, the compressive of cement stone in 6 h as the strength examining index can be designed in optimization test using the orthogonal method. The optimum formula determined by orthogonal was as follows: the weight of organic acids D is 1.0% based on cement，the weight of alcohols amines E is 0.04%，the weight of nitrates F is 4%. Under the optimum proportion, and the performance test of early strength agent LL was carried out after its addition of 2.5% in the cement. The ratio of the thickening time of early strength agent LL slurry to cement slurry is 0.436 less than 0.5, and the compressive strength of cement stone 6 h (39 ℃ and atmospheric pressure) is 11.0 MPa more than 4.0 MPa, they are all meeting the requirement of early strength agent industry standard SY/T5504.4—2008. And it has a good compatibility with the homemade retarders MAM, dispersants FASA and fluid loss AS.