The hairpin vortex packets structure and characteristic scale in the later stage of bypass transition induced by cylinder wake are investigated by TR PIV technique for both the side-view and top-view cases. The two-dimensional velocity components are correlated with λci criterion, and linear stochastic estimation is used to estimate the conditional average of the velocity field. For the side-view case, the conditionally averaged structure consists of a series of swirling motions located along a line inclined at a larger angle （17°） from the wall, and a low-speed region occupied by cylinder wake appearing right above it in the free stream. In the （x, z）-plane at the top of the log layer （y/δ = 0.2）, the dominant motions are shown to be large-scale regions of low momentum elongated along the streamwise and within a spanwise width of 0.555, which are consistently bordered by small-scale counter-rotating vortex pairs organized in the streamwise. The results suggest that in the later part of the transition zone, due to the upward induction of wake vortex, the hairpin vortex packets statistically perform a skeleton frame of larger scale and robust physique.%基于TR-PIV技术，通过侧视和俯视两种情况对圆柱尾迹影响下旁路转捩末期发卡涡涡包的结构及特征尺寸进行了实验研究．结合二维空间子波变换和λci准则，运用线性随机估计方法对速度信号进行条件平均．在侧视情况下，条件平均结果显示，在边界层中一系列发卡涡涡头与壁面构成17°的倾角，并且被尾迹涡所占据的低速区域出现在涡包上方的主流区中．在俯视的结果中，沿流向方向拉伸（流向尺度3δ，展向尺度0．555）的低速条带结构出现在法向高度为y／δ=0．2的流向一展向平面中，并且在该低速条带的两侧对称地出现了沿流向分布的反向旋转的涡结构．可以得出：在圆柱尾迹影响下旁路转捩的末期，由于尾迹涡诱导作用的影响，发卡涡涡包在形态上显示出了更大尺度的特征．
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