在UITabBarController.m 附上如下代码即可修改系统tabBar的高度。

- (void)viewDidLayoutSubviews {

    [super viewDidLayoutSubviews];

    CGRect frame = self.tabBar.frame;

    frame.size.height = 65;

    frame.origin.y = self.view.frame.size.height - frame.size.height;

    self.tabBar.frame = frame;

    self.tabBar.backgroundColor = [UIColor blackColor];

    self.tabBar.barStyle = UIBarStyleBlack;

}