方法一：

    NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:@"查看所有中奖记录"];
    NSRange strRange = {0,[str length]};
    [str addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:strRange];
    [_awardDisplayBtn setAttributedTitle:str forState:UIControlStateNormal];

HyperlinksButton.h

#import <UIKit/UIKit.h>

@interface HyperlinksButton : UIButton
{
    UIColor *lineColor;
}
-(void)setColor:(UIColor*)color;
@end

HyperlinksButton.m 

#import "HyperlinksButton.h"

@implementation HyperlinksButton

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        
    }
    return self;
}

-(void)setColor:(UIColor *)color{
    lineColor = [color copy];
    [self setNeedsDisplay];
}


- (void) drawRect:(CGRect)rect {
    CGRect textRect = self.titleLabel.frame;
    CGContextRef contextRef = UIGraphicsGetCurrentContext();
    
    CGFloat descender = self.titleLabel.font.descender;
    if([lineColor isKindOfClass:[UIColor class]]){
        CGContextSetStrokeColorWithColor(contextRef, lineColor.CGColor);
    }
    
    CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + textRect.size.height + descender+1);
    CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender+1);
    
    CGContextClosePath(contextRef);
    CGContextDrawPath(contextRef, kCGPathStroke);
}
@end