//下面的代码在一个窗体了放了一个flowLayoutPanel和一个dataGridView控件已经测试成功.
        //FlowLayoutPanel,DataGridView的dock属性都不设置,也就是默认值none
        private void Form1_Load(object sender, EventArgs e)
        {
            this.flowLayoutPanel1.Height = this.Height;
            this.flowLayoutPanel1.Width = this.Width;
            this.flowLayoutPanel1.Top = 0;
            this.flowLayoutPanel1.Left = 0;

            //这里的dataGridView1的高度和宽度减去的数值是为了保证,dataGridView1出现滚动条.
            this.dataGridView1.Height = this.flowLayoutPanel1.Height-40;
            this.dataGridView1.Width = this.flowLayoutPanel1.Width - 15;
            this.dataGridView1.Top = 0;
            this.dataGridView1.Left = 0;
        }

        private void Form1_Resize(object sender, EventArgs e)
        {
            this.flowLayoutPanel1.Height = this.Height;
            this.flowLayoutPanel1.Width = this.Width;

            this.dataGridView1.Height = this.flowLayoutPanel1.Height - 40;
            this.dataGridView1.Width = this.flowLayoutPanel1.Width - 15;
        }

------解决方案--------------------
你必须设置flowLayoutPanel和dataGridView的Anchor属性,要两个都设置

你再试试.不需要单独再在事件里写了

我刚试了,你说的问题不存在.