Abstract: Due to discontinuity of hard threshold at the threshold，there are some oscillation when reconstructing the image，there is the constant deviation between wavelet coefficients and the true value after soft threshold denoising，which will obscure the image edges and details.The hyperbolic functions is used into wavelet threshold denoising method，according to the different parameters，two different threshold function can be constructed，and the continuity at the threshold place is solved，and the deviation between the wavelet coefficients and the real value is eliminated，the noise is removed while maintaining good image edges and details.

Key words: hyperbolic functions, wavelet threshold denoising method, hard threshold, soft threshold

摘要： 小波硬阈值去噪由于在阈值处不连续，在重构时会出现振荡；软阈值处理后的小波系数与真实值之间存在恒定的偏差等情况，重构时会模糊图像的边缘和细节。将双曲线函数引入小波阈值去噪法，根据参数选择的不同可构造出两种不同的阈值函数，解决了阈值处的连续性问题，并在一定程度上消除阈值处理后小波系数与真实值之间的偏差，在去除噪声的同时，很好地保持了图像的边缘和细节。

关键词: 双曲线函数, 小波阈值去噪法, 硬阈值, 软阈值